xdt99: TI 99 Cross-Development Tools

The TI 99 Cross-Development Tools (xdt99) are a suite of programs that facilitate the development of programs for the TI 99 family of home computers and other TMS9900-based systems on modern computer systems.

As of this release, the cross-development tools comprise

All programs are written in Python and thus run on any platform that Python supports, including Linux, Windows, and macOS.

Additionally, xdt99 provides TI-specific editor support for some freely available development environments:

The plugins offer syntax highlighting, source navigation, and semantic renaming for assembly, GPL, and TI (Extended) BASIC programs. Note, however, that both plugins currently support an older version of the xas99 syntax.

To get started, follow the installation instructions and read the tutorial.

xdt99 is released under the GNU GPL version 3. The latest binary release as well as all sources are available on GitHub.

The xdt99 homepage always hosts the latest version of this document.

Installation

The latest xdt99 binary release is available on GitHub. Experienced users may also clone the xdt99 repository instead. The repository contains some additional test cases that are useful when extending or modifying xdt99.

xdt99 requires a working installation of Python 3.6 or later. On most Linux systems, Python is available as a package. For other platforms, we recommend installing the latest stable Python 3 release. Please note that xdt99 will not run on Python 2.

All xdt99 files should be placed somewhere in the $PATH or where the command-line interpreter will find them. Windows users will find Windows- specific instructions in the Windows Guide.

Additionally, the ide/ directory contains the editor plugins for GNU Emacs and IntelliJ IDEA. Please refer to the ide/README.md file for further information about editor support.

The example/ directory contains some sample files that are used throughout this manual.

Tutorial

The xdt99 tools lack a graphical user interface, and use the command line instead. While this choice will undoubtedly steepen the learning curve for some users, the command line is ultimately very suited for repetitive tasks, as encountered while developing assembly and GPL programs.

This section contains a hands-on introduction to using xdt99 to assemble programs, work with disk images and files, and run the results in an emulator and on real iron.

Commands to be typed in by the user are prefixed by $. If necessary, an additional Windows command prefixed by > is shown (for an example, see the Windows Guide). The sample outputs shown here originate from a Linux system and may look slightly different on other platforms.

For all examples, we use files in the example/ directory distributed with xdt99.

Using the Cross-Assembler

The file ashello.asm contains a simple assembly program in classic syntax. When using the xas99 cross-assembler in base mode, it translates source code into object code.

$ xas99.py -R ashello.asm

This command creates a new file ashello.obj. It also issues a warning about unresolved references

> --- <L> **** -
***** Warning: Unresolved references: VSBW, VMBW, KSCAN, VWTR

which we can ignore for now. In fact, we will hide warnings from now on, unless we want to discuss them.

The -R is a so-called option that tells xas99 to use registers with an R prefix instead of plain numerical values, just like the R option of the Editor/Assembler.

Invoking xas99 without any arguments

$ xas99.py
usage: xas99.py [-h] [-b | -i | -c | -t [<format>] | --embed-xb]
                [-l <file> [<file> ...] | -ll <file> [<file> ...]] [-5] [-18]
                [-s] [-n <name>] [-R] [-C] [-L <file>] [-S] [-E <file>] [-q]
                [-a <addr>] [-I <paths>] [-D <sym=val> [<sym=val> ...]]
                [-o <file>]
                [<source> [<source> ...]]
xas99.py: error: One of <source> or -l/-ll is required.

lists all available options and their expected parameters, if any. Options enclosed in brackets [] are optional, and options separated by | are mutually exclusive.

The help option -h also lists all available options, but includes a short description for each.

$ xas99.py -h
...
TMS9900 cross-assembler, v3.0.0

positional arguments:
  <source>              assembly source code(s)

optional arguments:
  -h, --help            show this help message and exit
  -b, --binary          create program binaries
...

Each option has a short form and a long form, e.g., -h and --help, which may be used interchangeably.

As we can see, some options take one or more additional arguments. Arguments are strings, e.g., for -L, or numerical, e.g., for -a. Numerical arguments may be decimal or hexadecimal if prefixed by > or 0x. Note that the > character is used for output redirection on all platforms, so the entire argument needs to be quoted, e.g.,

$ xas99.py -R -a ">2000" ashello.asm

If an option can take more than one argument, such as -D, they are separated by spaces.

$ xas99.py sample.asm -D x=1 y=2 z=3

If an option is shown as -x <arg> [<arg> ...] in the usage help, we know that it takes one or more arguments.

The order of options and any other parameters such as ashello.asm is generally not important, but any arguments must always stay together with their option. There is, however, one caveat, which we will discuss later.

Coming back to the assembly run (let’s rerun it without -a)

$ xas99.py -R ashello.asm

the resulting file ashello.obj contains uncompressed object code, which looks like this:

$ cat ashello.obj
> type ashello.obj
0007EASHELLO A0000B100DB4845B4C4CB4F20B574FB524CB4420B2020B68697F19FF       0001
A0012B7420B616EB7920B6B65B7921B0300B0000B02E0B8300B04C0B02017F2F9F          0002
A0028B2A20B0202B0300B0420B0000B0580B0602B16FBB0200B0043B02017F336F          0003
A003EC0002B0202B001AB0420B0000B0208BFF00B04C9B0300B0002B10007F31FF          0004
A0054B0300B0000BD809B837CBD809B8374B0420B0000B9220B8375B13F97F2D4F          0005
A006ABD020B8375B0980B0240B000FB0260B0700B0420B0000B10E87F410F               0006
5001CSTART 30030VSBW  30046VMBW  3007AVWTR  30062KSCAN 7F2F8F               0007
:       xdt99 xas                                                           0008

We can load this file with the Editor/Assembler cartridge using option 3, or alternatively with the TI Extended BASIC module using the CALL LOAD statement.

Uncompressed object code is not an efficient program format, though. If compatibility with Extended BASIC is not required, generating compressed object code with option -C reduces both size and loading time:

$ xas99.py -R -C ashello.asm -o ashello-c.obj

In order to not overwrite our already existing ashello.obj file, we overrode the default output filename with the output option -o.

Compressed object code contains unprintable characters, but if we replace those by ., we can show the contents:

..~ASHELLO A..B..BHEBLLBO BWOBRLBD B  BhiBt BanBy BkeBy!B..B..B..B..B..B..B* F
A.*B..B..B. B..B..B..B..B..B.CB..C..B..B..B. B..B..B..B..B..B..B..B..B..B..F
A.ZB.|B..B.tB. B..B. B.uB..B. B.uB..B.@B..B.`B..B. B..B..F
5..SLOAD 5..SFIRST5.~SLAST 5..START 3.zVWTR  F
3.FVMBW  3.0VSBW  3.bKSCAN F
:       xdt99 xas 

Comparing both object files, we see that the size of the compressed version is only about three fifths of that of the uncompressed file:

$ ls -l ashello*.obj
> dir ashello*.obj
-rw-rw---- 1 ralph ralph 400 Jul 12 09:58 ashello-c.obj
-rw-rw---- 1 ralph ralph 640 Jul 12 09:58 ashello.obj

As stated above, ashello.asm uses classic syntax, i.e., the syntax used by the Editor/Assembler. xas99 also supports a modern, more relaxed syntax, which allows for lowercase, additional whitespace, and longer labels, and features new directives and a preprocessor with conditional assembly and macros.

For an example of the new syntax, please refer to file ashello_new.asm, which yields the same object code as ashello.asm.

The list file or listing provides insight into the assembled program by showing where each assembled instruction is placed in memory. List files are thus particularly useful during development.

Similar to the Editor/Assembler, we create list files using the list option -L, followed by a filename:

$ xas99.py -R ashello.asm -L ashello.lst

This command yields a text file ashello.lst that begins like this:

XAS99 CROSS-ASSEMBLER   VERSION 3.0.0
     **** ****     > ashello.asm
0001               *  HELLO WORLD
0002
0003                      IDT 'ASHELLO'
0004
0005                      DEF SLOAD,SFIRST,SLAST,START
0006                      REF VSBW,VMBW,VWTR
0007                      REF KSCAN
0008
0009 0000 100D  14        JMP  START
0010
0011      8300     WRKSP  EQU  >8300
0012      8374     KMODE  EQU  >8374
0013      8375     KCODE  EQU  >8375
0014      837C     GPLST  EQU  >837C
0015
0016 0002 4845     MESSG  TEXT 'HELLO WORLD'
     0004 4C4C
     0006 4F20
     0008 574F
     000A 524C
     000C 44
0017 000D   20            TEXT '   hit any key!'
     000E 2020
     0010 6869
     0012 7420
     0014 616E
     0016 7920
     0018 6B65
     001A 7921
0018      001A     MESSGL EQU  $-MESSG
0019
0020 001C 0300  24 START  LIMI 0
     001E 0000
0021 0020 02E0  18        LWPI WRKSP
     0022 8300
...

The four columns before the source code show

Some directives such as EQU do not generate machine code, so their second and third columns may be missing or show different information.

For more complex programs with COPY and/or macros, source indicators show to which source file a certain listing sequence belongs to:

XAS99 CROSS-ASSEMBLER VERSION 3.1.0 **** **** > asmacs.asm … **** **** > MAC0 … **** **** > DSK2.ASCOPY3 … < MAC0 … < asmacs.asm …

In addition to option 3 object code, xas99 can also generate images for E/A option 5 using the image option -i.

$ xas99.py -R -i ashello.asm -o ashello5.img

Again, we override the default output name ashello.img, for later. The resulting image file ashello5.img has 248 bytes and contains binary data.

$ ls -l ashello5.img
> dir ashello5.img
-rw-rw---- 1 ralph ralph 132 Jul 12 13:11 ashello5.img

To view the binary data, we can create a hexdump of the file.

$ hexdump -C ashello5.img
> Format-Hex ashello5.img            (using Powershell version 5 or higher)
00000000  00 00 00 84 a0 00 10 0d  48 45 4c 4c 4f 20 57 4f  |........HELLO WO|
00000010  52 4c 44 20 20 20 68 69  74 20 61 6e 79 20 6b 65  |RLD   hit any ke|
00000020  79 21 03 00 00 00 02 e0  83 00 04 c0 02 01 2a 20  |y!............* |
00000030  02 02 03 00 04 20 00 00  05 80 06 02 16 fb 02 00  |..... ..........|
00000040  00 43 02 01 a0 02 02 02  00 1a 04 20 00 00 02 08  |.C......... ....|
00000050  ff 00 04 c9 03 00 00 02  10 00 03 00 00 00 d8 09  |................|
00000060  83 7c d8 09 83 74 04 20  00 00 92 20 83 75 13 f9  |.|...t. ... .u..|
00000070  d0 20 83 75 09 80 02 40  00 0f 02 60 07 00 04 20  |. .u...@...`... |
00000080  00 00 10 e8                                       |....|

The first column shows the byte offset of the line, the wide second column shows the byte values, and the third column shows the textual representation of the bytes, where non-printable characters are shown as .. All values are in hexadecimal.

For reasons explained in section E/A Utility Functions, this file will might crash when run. xas99 even reminds us that some utility functions are missing.

> --- <L> **** -
***** Warning: Unresolved references: VSBW, VMBW, KSCAN, VWTR

We can ignore this warning only for object code, i.e., for E/A option 3 programs. To add the missing functions to our image, we need to assemble with this command:

$ xas99.py -R -i ashello.asm vsbw_ea.asm vmbw_ea.asm vwtr_ea.asm kscan_ea.asm

The additional files provide the unresolved symbols. Thus, our revised command does not print any warnings.

Another, more common way to provide required E/A utility functions is to COPY them in the source code. For example, we could modify ashello.asm to look like

...
       ORI  R0,>0700
       BLWP @VWTR

       JMP  NEXT

       COPY "vsbw_ea.asm"          |
       COPY "vmbw_ea.asm"          |   add these lines
       COPY "vwtr_ea.asm"          |   to provide utilities
       COPY "kscan_ea.asm"         |

       END

Note that both methods, command line files and COPY, yield identical output files.

Using Emulators and Real Iron

To run either of the generated programs with the MAME emulator, we require a disk image containing these files. We can create this image (and more) with the xdt99 Disk Manager xdm99.

The example/ directory contains an empty SS/SD image work.dsk that we will use. Invoking xdm99 with the disk image filename displays the disk properties and contents.

$ xdm99.py work.dsk
WORK      :     2 used  358 free   90 KB  1S/1D 40T  9 S/T
----------------------------------------------------------------------------

We see that the disk image with the name WORK has 2 used and 358 free sectors, has a capacity of 90 KB and is a formatted as one-sided, single density with 40 tracks and 9 sectors per track. Note that 2 sectors are always reserved for disk information and the catalog.

We can add files to the disk image with the add option -a, generally together with the format option -f.

$ xdm99.py work.dsk -a ashello.obj -f DIS/FIX80
$ xdm99.py work.dsk -a ashello5.img

The format is one of the known TI file formats and may be specified rather loosely, e.g., INTVAR 254, DF80, PROGRAM, P, etc. If we use a space in the format, we need to quote it, e.g., -f "D/F 80".

If no format is given, PROGRAM type is assumed, and if the record length is omitted, a record length of 80 is used.

If we add a single file to a disk image, we can also override the TI filename on the disk with the name option -n.

Our disk image now contains two files:

$ xdm99.py work.dsk
WORK      :     8 used  352 free   90 KB  1S/1D 40T  9 S/T
----------------------------------------------------------------------------
ASHELLO       4  DIS/FIX 80     672 B   8 recs     2020-03-25 12:13:22 C
ASHELLO5      2  PROGRAM        248 B              2020-03-25 12:13:26 C

Should we have no blank disk image available, we can create a new image with the initialize option -X:

$ xdm99.py -X sssd work.dsk

The disk size can be descriptive like SSSD, 2s/2d, 1s1d80t, or CF, or explicit by specifying the number of sectors, e.g., 720. The maximum size for a disk image is 1600 sectors.

We can also combine the creation of a new image, and the addition of files into a single operation.

$ xdm99.py -X sssd work.dsk -a ashello.obj -f df80
$ xdm99.py work.dsk -a ashello5.img

It’s possible to list multiple files after the -a option if they all share the same file type. This is not the case here, though, so we need two commands to accomplish our task.

We can use this disk with MAME to load our files with an emulated Editor/ Assembler cartridge. (Make sure to type all of this in one line!)

$ mame64 ti99_4a -ioport peb -ioport:peb:slot2 32kmem -ioport:peb:slot8 hfdc
         -ioport:peb:slot8:hfdc:f1 525dd -cart EA.rpk -flop1 work.dsk

You’ll probably need to adjust the name of the Editor/Assembler cartridge image EA.rpk to match your installation. Alternatively, we could load both E/A and the disk image using the MAME UI.

In the emulated Editor/Assembler, we select option 3, LOAD AND RUN, and enter the name of the object code file at the FILE NAME? prompt:

DSK1.ASHELLO

Once the loader finishes, we type START at the PROGRAM NAME? prompt. The words HELLO WORLD should appear on screen. Pressing any key will change the color of the screen border.

Next, we quit the program by hitting FCTN-= and start Editor/Assembler again. We now select option 5, RUN PROGRAM FILE, and enter the name of our image file,

DSK1.ASHELLO5

The program will start automatically. To quit MAME, press Esc; if that does not work, press ScrLock and then Esc.

If we want to use the Classic 99 emulator, we could also use our disk image, even though the emulator cannot write to disk images. The native format of Classic 99 are so-called files in a directory (FIAD) in TIFILES format.

xdm99 can convert plain files and files on disk images into TIFILES format by using the TIFILES options -T and -t, resp.

For plain files, -T converts one or more files into TIFILES format. Unless we are creating files of type PROGRAM, we also have to provide the file type option -f.

$ xdm99.py -T ashello5.img
$ xdm99.py -T ashello.obj -f DIS/FIX80
$ ls -l *.tfi
> dir *.tfi
-rw-rw---- 1 ralph ralph 384 Mär 25 18:31 ashello5.img.tfi
-rw-rw---- 1 ralph ralph 896 Mär 25 18:31 ashello.obj.tfi

By default, the converted files will have an additional .tfi extension. In our case, we want upper-case filenames without extension for Classic 99, so we’re using the -o option again.

$ xdm99.py -T ashello.obj -f DIS/FIX80 -o ASHELLO
$ xdm99.py -T ashello5.img -o ASHELLO5

We can examine the stored metadata of TIFILES or v9t9 files by using the info option -I.

$ xdm99.py -I ASHELLO
ASHELLO       4  DIS/FIX 80     672 B   8 recs     2020-03-25 18:32:24 C

To convert in the other direction, we use the “from TIFILES” option -F:

$ xdm99.py -F ASHELLO -o ashello.obj

The conversion becomes even simpler if we use our disk image instead of plain files. The extract option -e will create a local copy of a file stored on the disk image. If we combine -e with the TIFILES option -t, the local file will be in TIFILES format.

$ xdm99.py work.dsk -t -e ASHELLO -o ASHELLO
$ xdm99.py work.dsk -t -e ASHELLO5 -o ASHELLO5

To convert in the other direction, we still use -t, but combine it with the add option -a. This implies that we should use plain files for disk images and TIFILES format for files not stored in disk images.

Note that when using options that accept more than one argument, such as -a or -e, the position of non-option arguments such as work.dsk becomes important. For example, if we rewrote the previous command into

$ xdm99.py -t -e ASHELLO ASHELLO5 work.dsk

xdm99 would not know that work.dsk is our disk image instead of another file to extract. Thus, always keep multi-argument options after any non-options, like we do in this manual.

We can now copy both files ASHELLO and ASHELLO5 into the DSK1 directory of Classic 99, start the emulator, and select the Editor/Assembler from the menu. All further steps are then similar to the MAME description above.

If we want to run our sample programs on a real TI 99 using the nanoPEB/CF7+ or the HxC floppy emulator, we need to transfer our disk image to a CF or SD card first. In the case of the nanoPEB/CF7+, we use the xvm99 volume manager.

$ xvm99.py /dev/sdc 2 -w work.dsk

Assuming a CF card is connected to our computer, this command will store the disk image work.dsk as volume 2, where it can be accessed on the TI 99 with CALL MOUNT(n,2).

The /dev/sdc is the Linux device the CF card is connected to on our computer. To get the name of the device to use on a Linux machine, we can use the fdisk -l command, but we need some experience to identify the CF card.

If we’re running Gnome or KDE, we can also mount the CF card and then view the card properties. With KDE, the device name is listed under Mounted from.

On macOS systems, the diskutil list lists all devices. We pick the device name from the first column.

For Windows systems, we can use the wmic command (no admin rights required):

> wmic diskdrive list brief
Caption                            DeviceID            Model                      ...
VBOX HARDDISK ATA Device           \\.\PHYSICALDRIVE0  VBOX HARDDISK ATA Device   ...
Generic- Compact Flash USB Device  \\.\PHYSICALDRIVE2  Generic- CF USB Device     ...
Generic- SD/MMC USB Device         \\.\PHYSICALDRIVE1  Generic- SD/MMC USB Device ...
Generic- xD-Picture USB Device     \\.\PHYSICALDRIVE3  Generic- xD USB Device     ...   

Here, we see that the USB CF Card reader is connected to \\.\PHYSICALDRIVE2.

We can also transfer single files if the target volume already contains a disk image. To check this, we can get the status of a volume by invoking xvm99 without options. If there is no image, we get

$ xvm99.py /dev/sdc 2
[   2]  (not a valid disk image)

If volume 2 contains a valid disk image, we will see a short summary instead.

[   2] PROGRAMS3 :  1248 used   352 free

In the latter case we can add files to a volume by using the same syntax as for xdm99.

$ xvm99.py /dev/sdc 2 -a ashello.obj -f DIS/FIX80
$ xvm99.py /dev/sdc 2 -a ashello5.img

Either way, our two programs are now available in volume 2 and can be loaded on a TI 99 with a nanoPEB or CF7+.

Note that the volume can also be a list, e.g., 1,3 or a range, e.g., 1-3. Any commands are then applied to all volumes specified. For example,

$ xvm99.py /dev/sdc 1,3-5 -a LICENSE -f DV80

will add the file LICENSE to volumes 1, 3, 4, and 5, assuming that each volume contains a valid disk image.

For a HxC drive made by Lotharek, we need to convert the disk image to HFE format. This is the job of the xhm99 HFE image manager.

To convert a disk image to HFE format, we use the “to HFE” option -T.

$ xhm99.py -T work.dsk

yields the HFE file work.hfe which we can copy onto an SD card and then insert that into the HxC drive.

We can also check the contents of our HFE disk ty typing

$ xhm99.py work.hfe
WORK      :     8 used  352 free   90 KB  1S/1D 40T  9 S/T
----------------------------------------------------------------------------
ASHELLO       4  DIS/FIX 80     672 B   8 recs     2020-03-25 12:13:22 C
ASHELLO5      2  PROGRAM        248 B              2020-03-25 12:13:26 C

To convert in the other direction, we would use the “from HFE” option -F.

Other Cross-Assembler Formats

After this foray into managing disks and files of various formats, let’s return to xas99 now. The cross-assembler not only generates code for the Editor/Assembler cartridge, but also raw binary code and MAME-style cartridges, which can be used independently of E/A.

The cartridge option -c automatically generates a GPL header and then assembles everything into a MAME-style cartridge RPK archive.

$ xas99.py -R -c ascart.asm -n "HELLO CART"

Note that ascart.asm does not make use of VDP utilities, so we don’t have to include them on the command line.

The name option -n sets the program name that shows up in the TI menu screen. Since our name contains a space, we need to quote the entire name. If no name is given, the filename without extension is used.

In order to add the GPL header, the source program must not use memory range >6000 to >6030. We can ensure this by using either an AORG >6030 or higher directive or an RORG directive at the beginning of the program. In case of using RORG, xas99 automatically relocates the code to address >6030.

Additionally, the first instruction of the original source code must be executable, just like for option 5 programs, unless the program uses an END directive with label, pointing to the start address (see ascart.asm).

As an aside note, we can manually relocate the relocatable segments of a program with the rebase option -a. Thus, if a program is placed with only RORG, we can use -a to move it to any memory address.

The resulting file with extension .rpk can be used as-is with the MAME emulator:

$ mame64 ti99_4a -cart ascart.rpk

In MAME, the TI menu screen will show 2 HELLO CART, and pressing 2 will run the (trivial) sample program. Note that the programs runs without the 32K memory expansion, as the program code is stored entirely inside the cartridge ROM.

Generating cartridge images with option -c is recommended only for very simple programs, since the capabilities of the generated GPL header are limited, and the resulting .rpk file can only be used for MAME.

A more general approach is to write the GPL header yourself and then to assemble the program with the binary option -b.

$ xas99.py -R -b ascart_hdr.asm

The resulting binary file ascart_hdr.bin corresponds to an “executable” on other platforms and contains only machine code, without any headers or padding. It can be used as cartridge file for Classic 99, or put on a multi-cart or Flash cart such as the FlashROM or the FinalGROM.

The -b option is not limited to cartridges. We can also use it to create DSRs, or code we want to load dynamically into memory, e.g., by DSR opcode 5. We can put the binaries in an EPROM, or store them in a microcontroller or FPGA. As such, binary is arguably the simplest, and most versatile format.

E/A Utility Functions

As we now know how to assemble programs into various formats, we should briefly discuss the use of E/A utility functions in each case. These functions, such as VSBW, VMBR, or VWTR simplify the access to VDP memory and are thus used in most assembly programs.

When creating object code for E/A option 3, the Editor/Assembler provides all utilities listed in the E/A manual automatically. To use any function, we only need to import its name with a REF directive, and can then call the function with BLWP.

ref  vsbw
...
li   r0, 160
li   r1, >4000
blwp @vsbw

Remember the warning we got when assembling ashello.asm? That was because we REFed utility VSBW, but the function was not part of our code. In case of option 3, this is fine, as the function is actually provided by E/A itself.

For other output formats, including E/A option 5, E/A does not supply utilities, so we must include them in our program. For this, xas99 provides a variety of utilities in the lib/ directory. To use any function, we must COPY it into our source, and can then call it with BL.

li   r0, 160
li   r1, >4000
bl   @vsbw
...
copy "vsbw.asm"

Note that COPY will automatically search the lib/ directory, so we don’t need to include the lib/ path with -I.

An alternative way to use functions from lib/ is to reference their names in the code

ref  vsbw
...
li   r0, 160
li   r1, >4000
bl   @vsbw

and then include their source files on the command line:

$ xas99.py -R -i program.asm vsbw.asm

As the name of the resulting file is the name of the first source file given, we should keep our main program before any utilities. xas99 will search for sources automatically in the lib/ directory, so we don’t need to provide the full path for vsbw.asm.

In the examples above, we used some E/A-compatible functions, which are still called by BLWP. We can identify these functions in lib/ by their _ea suffix. Just as the original E/A utilities, these _ea functions use >2094 as their workspace base.

The lib/ directory also contains some functions not provided by E/A, such as VWWT or VMZW. Please refer to lib/README.md for a description of each function.

Linker

The last xas99 feature we want to cover here is linking. The linker is an optional part of xas99 that will join multiple object code files together. In this process, the linker will find a memory layout for all program segments, and match the list of REF symbols with the list of DEF symbols.

To invoke the linker and join multiple object code files together, we use the link option-l.

$ xas99.py -l part1.obj part2.obj -o whole.obj

We can choose any output format for the linked code, i.e., we can combine -l with -b, -i, -c, -t, or none of those if we want to keep the object code format.

We can also link some object code files to the assembled results of some source files. In fact, if part1.obj and part2.obj are the object code files of source files part1.asm and part2.asm, resp., then these three commands are equivalent and yield three identical files whole.obj.

$ xas99.py -l part1.obj part2.obj -o whole.obj
$ xas99.py part1.asm -l part2.obj -o whole.obj
$ xas99.py part1.asm part2.asm -o whole.obj

Note, however, that

$ xas99.py part2.asm -l part1.obj -o whole.obj

will yield a different file, since the order of files is preserved in the final layout of whole.obj. Also keep in mind that any files to the right of -l must be object code files.

So what is the actual difference between joining object code files with -l and joining source code files with COPY? When joining sources, each source file sees all the symbols of the other sources, which requires care to not create symbol conflicts. When joining object code, on the other hand, each unit only sees the symbols exported by the other files exported with DEF and imported with REF, limiting the chance of symbol conflicts.

For example, linking the object code of program 1

     def  s2, s3
s1   equ  101
s2   mov  r11, r10
     ...
     b    *r10
s3   data >1234

and the object code of program 2

     ref s3
s1   equ  202
s2   mov  @s3, r0
     ...

does not create a symbol conflict, since s1 is local to each program, s2 is not imported by program 2, and s3 is only defined by program 1.

There is also a historical reason for favoring linking over copying. With the Editor/Assembler, for example, assembling takes much more time than linking. Thus, it is more economical to break programs into small units so that during development, we can make changes to only some units, assemble those units, and link everything together, which is much faster than assembling everything for every little change.

Luckily, with today’s computers being unimaginably faster, we can choose either method without worrying about performance. Thus, it is merely a personal choice which method we choose.

Creating GROM Cartridges

In this section, we use the xga99 GPL cross-assembler to assemble GPL programs into cartridge images that run in any emulator or, with appropriate hardware such as the FinalGROM, on real hardware.

To get started, we use xga99 to assemble the gahello.gpl GPL program from the examples/ directory:

$ xga99.py gahello.gpl

The resulting file gahello.gbc contains GPL byte code, which corresponds to the binary format created by xas99.py with the -b option.

$ hexdump -C gahello.gbc
> Format-Hex gahello.gbc             (using Powershell version 5 or higher)
00000000  ff ff ff ff ff ff ff ff  00 00 00 00 00 00 00 00  |................|
00000010  ff ff ff ff ff ff ff ff  34 46 6a ad dc c5 5e e3  |........4Fj...^.|
00000020  34 46 6a ad dc c5 5e e3  63 38 00 80 0f 30 00 84  |4Fj...^.c8...0..|
00000030  01 87 00 80 0f 82 00 84  01 d0 0c 12 12 0c 02 02  |................|
00000040  0c 00 00 00 00 00 00 00  00 00 30 48 48 30 08 08  |..........0HH0..|
...
00000150  ff 87 02 05 00 ff be 10  80 03 61 61 92 10 41 59  |..........aa..AY|
00000160  00 0b                                             |..|

Note that xga99 does not support relocatable code, and cannot create GPL object code.

GPL byte code is the native format for GROMs, so we can use gahello.gbc right away with the FinalGROM if we rename the file to something ending in G, for example, gahellog.

Other hardware, such as the GRAM Kracker, also use GPL byte code files, but additionally expect some header information xga99 currently not provides.

For the MAME emulator, we cannot use .gbc files directly, but we can use them to build an RPK cartridge archives.

Alternatively, xga99 supports the creation of cartridges with automatically generated GPL headers using the cartridge option -c:

$ xga99.py -c gahello.gpl

Again, the memory area >6000->6030 is reserved for the generated GPL header. To place code at some particular address, we use the GROM directive to choose the GROM, and then optionally the AORG directive to define an offset relative to the start of the GROM. GROM supports both GROM numbers 0, 1, …, 7 and GROM base addresses >0000, >2000, …, >E000.

The result of this command is a .rpk file we can use with MAME:

$ mame64 ti99_4a -cart gahello.rpk

The emulated TI menu screen will show our program as GAHELLO. We can override that name with the name option -n.

Again, we recommend using -c only for simple cases, and working with GPL byte code otherwise.

When we create GPL programs for the FinalGROM, we need to make sure to assemble to GPL byte code and to rename the resulting .gbc file so that it ends in G and has a .bin extension. Otherwise, the FinalGROM will erroneously assume that the file contains TMS9900 machine code.

Working with BASIC Programs

TI BASIC and TI Extended BASIC programs are usually entered in listing format, i.e., as text. Internally, however, BASIC programs are stored in token format, which is a binary format. Disks and cassettes also store the internal format.

The xbas99 BASIC tool can convert TI BASIC and TI Extended BASIC programs from one format into the other format.

The TI BASIC program nim.bas in the examples/ directory is in listing format, just as if we typed it in from a home computer magazine from the 80s. To convert this into a program we can load and run in TI BASIC, we must tokenize the listing with the create option -c.

$ xbas99.py -c nim.bas

To run the resulting file nim.prg in an emulator, we again create a disk image

$ xdm99.py basic.dsk -X sssd -a nim.prg

and start the MAME emulator with it (again, as one line)

$ mame64 ti99_4a -ioport peb -ioport:peb:slot8 hfdc
         -ioport:peb:slot8:hfdc:f1 525dd -flop1 basic.dsk

In TI BASIC, we can then load and run our Nim program from DSK1.

OLD DSK1.NIM
RUN

It is important to know that xbas99 performs a “dumb” translation from listing to tokens – it does not perform a syntax check. As an example, this “program”

10 CALL PRINT A="X" / INPUT 1,2,3
20 LET IT BE

will tokenize with -c and load in TI BASIC (!) perfectly fine, but when we try to RUN it, the interpreter will throw an error:

* BAD NAME IN 10

When given a program in an internal format, such as our nim.prg, we can decode it into a textual format with the decode option -d.

$ xbas99.py -d nim.prg -o nim2.bas

Files nim.bas and nim2.bas should be identical.

We can also decode to stdout, i.e., print the decoded listing on the console with the print option -p.

$ xbas99 -p nim.prg
100 REM A VERSION OF NIM
110 PRINT :"THERE ARE 21 COINS ON THE"
120 PRINT "TABLE."
...

Again, -p <file> is equivalent to -d <file> -o -.

xbas99 does not distinguish between TI BASIC and TI Extended BASIC, so we must be careful not to use TI Extended BASIC keywords when developing a TI BASIC program.

Labels Replacing Line Numbers

xbas99 also supports a more modern way to write BASIC programs. Instead of using line numbers for each line,

210 X=X*2 :: Y=Y+1
220 IF X<10 THEN 210
230 ON Y GOTO 310,340,590
...
310 REM DO THIS
...
340 REM DO THAT
...
590 END

we can use labels for each line that is the target of a branch:

COUNT:
 X=X*2 :: Y=Y+1
 IF X<10 THEN @COUNT
 ON Y GOTO @DOTHIS,@DOTHAT,@DONE
...
DOTHIS:
 REM DO THIS
...
DOTHAT:
 REM DO THAT
...
DONE:
 END

A label must be alphanumeric and followed by a colon :. The actual program lines must be indented by at least one blank. Sadly, when using a label, e.g., as part of a GOTO statement, we must prefix the label with an @ sign. The @ prefix is needed to identify invalid, i.e., mistyped labels, or else invalid labels would become stray variables.

In order to tokenize a program with labels, the label option -l must be supplied. -l can only be used together with -c.

$ xbas99.py -c -l nim_labels.bas

Before tokenizing a program with labels, xbas99 will apply line numbers to the program similar to what the BASIC command RESEQUENCE 100,10 would do. Consequently, labels are not preserved in tokenized programs, so when we decode a tokenized program with labels, we get line numbers back:

$ xbas99.py -p nim_labels.prg
100 REM A VERSION OF NIM
110 PRINT :"THERE ARE 21 COINS ON THE"
120 PRINT "TABLE."
130 PRINT "BY TURNS, EACH PLAYER TAKES"
...

After tokenizing the program, xbas99 reports any unused labels, i.e., labels which are defined, but not used as targets.

Automation

We stated in the introduction of this tutorial, command line tools like xdt99 are suited for automation.

Let’s assume that we are developing an assembly program. That usually means that we write some part of the program, assemble it, test the new code in an emulator, fix the code or write the next part, and so on.

To simplify this cycle, we can write a script or batch file that will perform all of these tasks – except for writing code, of course – automatically.

In Linux or macOS, this sample bash file build.sh will assemble a file and start the MAME emulator.

#!/bin/sh
set -e
xas99.py prog1.asm prog2.asm -R -i -o program
xdm99.py -X sssd w.dsk -a "progra?"
mame64 ti99_4a -ioport peb -ioport:peb:slot2 32kmem -ioport:peb:slot8 hfdc \
       -ioport:peb:slot8:hfdc:f1 525dd -cart EA.rpk -flop1 work.dsk

Of course, you will have to adapt filenames and paths to your setup. Finally, set the executable flag for the file

$ chmod ug+x build.sh

The set -e ensures that the script aborts when one of the commands returns with an error. The assembler will create one or more image files program, progran, …, which we add to a newly created disk image using a wildcard. Finally, we start MAME with the E/A cartridge and the created disk image.

For Windows, we can adapt above script like this, and call it build.bat:

@echo off
xas99.py prog1.asm prog2.asm -R -i -o program
if %errorlevel% neq 0 exit /b
xdm99.py -X sssd w.dsk -a "progra?"
if %errorlevel% neq 0 exit /b
mame64 ti99_4a -ioport peb -ioport:peb:slot2 32kmem -ioport:peb:slot8 hfdc ^
       -ioport:peb:slot8:hfdc:f1 525dd -cart EA.rpk -flop1 work.dsk

The if %errorlevel% ... statements check if the previous command succeeded, and if not, abort the batch file.

For each development cycle, we then only need to run our script after each code change.

<edit prog1.asm or prog2.asm>
$ ./buid.sh
> build.bat
<edit prog1.asm or prog2.asm>
$ ./buid.sh
> build.bat
...

This automation by scripting becomes more effective the more steps the build process takes. The firmware of the FinalGROM cartridge, for example, comprises an assembly part and a GPL part, and each result is included in a C program, which is then compiled. Executing the individual steps in the correct order quickly becomes a too complex task to merely rely on pressing Cursor-Up the correct number of times in the command line.

From Here On

This concludes our short introduction to some xdt99 tools. For an in-depth description of each tool, please refer to the following sections.

xas99 Cross-Assembler

The xas99 two-pass cross-assembler translates TMS9900 and TMS9995 assembly code as well as programs for the F18A co-processor into executable programs for the TI 99 home computer, in a variety of formats.

All existing assembly sources for the TI 99 should cross-assemble using xas99 without modifications. Likewise, the generated object code is identical to the object code produced by the TI Editor/Assembler package. This includes all of its quirks, such as variable-length lines or redundant address tags, but hopefully none of its bugs.

Assembling Source Code

In standard mode, the xas99 cross-assembler reads an assembly source file and generates an uncompressed object code file that is suitable for the Editor/ Assembler option 3 loader.

$ xas99.py -R ashello.asm

This command yields object code file ashello.obj. We can override the output filename with the output option -o.

$ xas99.py -R ashello.asm -o HELLO-O

The special name - redirects the output to stdout, i.e., prints it on the screen.

$ xas99.py -R ashello.asm -o -
> --- <L> **** -
***** Warning: Unresolved references: VSBW, VMBW, KSCAN, VWTR
0007EASHELLO A0000B100DB4845B4C4CB4F20B574FB524CB4420B2020B68697F19FF       0001
A0012B7420B616EB7920B6B65B7921B0300B0000B02E0B8300B04C0B02017F2F9F          0002
A0028B2A20B0202B0300B0420B0000B0580B0602B16FBB0200B0043B02017F336F          0003
...
5001CSTART 30030VSBW  30046VMBW  3007AVWTR  30062KSCAN 7F2F8F               0007
:       xdt99 xas                                                           0008

The xas99 options -R for register prefixes, -L for creating a listing, -S for adding a symbol block to the listing, and -C for generating compressed object code correspond to the respective options of the Editor/Assembler.

$ xas99.py -R -C ashello,asm -L ashello.lst -S -o ashello-c.obj

xas99 will report any errors to stderr during assembly. A typical error may look like

> t.asm <2> 0002 -   jmp @y
***** Error: Invalid '@' found in expression

Shown are the filename containing the error, the pass in which the error occurred, the line number and the actual erroneous line, followed by the error message. Note that in some cases, an error may be reported twice, once for each pass.

At the end of assembly, if there were any errors, xas99 shows an error count so that users can quickly see if any errors occured (especially if color is disabled):

12 Errors found.

The assembler may also issue a number of warnings, e.g.,

> t.asm <2> 0002 -      mov  r0, >000a
***** Warning: Treating as register, did you intend an @address?
> t.asm <2> 0003 -      ci   r1, r2
***** Warning: Register R2 used as immediate operand
> t.asm <2> 0006 - lab  mov  @val(r1), r0
***** Warning: Using indexed address @0, could use *R instead
> --- <2> **** -
***** Warning: Unused constants: L1

Warnings indicate a likely error made by the developer. Warnings are also written to stderr, unless they are suppressed with the quiet option -q.

Note that all examples above issues a warning we omitted so far:

$ xas99.py -R ashello.asm
> --- <L> **** -
***** Warning: Unresolved references: VSBW, VMBW, KSCAN, VWTR

This warning lists all symbols imported by REF, for which no external symbol defined by DEF was found. Since all unresolved symbols are E/A utility functions, and we are creating object code for E/A option 3, we can ignore this warning. In all other cases, this warning indicates an error that might crash our program.

On Linux and macOS platforms, all warnings and errors are colored by default. Irrespective of platform, the use of color can be turned on or off by using the color options --color on or --color off, resp. (Technical note: Colors require so-called ANSI escape sequences, something that Windows cmd.exe only started to support very recently.)

Creating Program Images

The image option -i tells xas99 to generate image files that can be loaded using Editor/Assembler option 5.

$ xas99.py -R -i ashello.asm

Images larger than 8 KB are split automatically into multiple files, using the filename convention of the Editor/Assembler.

The -i option follows the SAVE utility program shipped with the Editor/ Assembler package, and honors the symbols SLOAD, SFIRST and SLAST to generate the image for the entire memory area spanned by those addresses.

Alternatively, if either symbol is missing, xas99 will generate separate image files for each program segment defined in the assembly source. For example, a source file containing

     AORG >A000
L1   B @L2
     AORG >B000
L2   B @L1

will yield two images files of 10 bytes each, instead of a single file of about 4 KB.

Note that the E/A option 5 loader happily loads non-contiguous image files, even though the original SAVE utility cannot generate such images.

For further control about the memory regions to include in the image, see the SAVE directive below.

We can use the base option -a to define the base address for relocatable code. If no base address is given, default address >A000 is used for images. For example, creating an image file from the source

data >1111
aorg >a002
data >2222
rorg 4
data >3333

will yield an image containing these bytes

00000000  00 00 00 0c a0 00 11 11  22 22 33 33              |........""33|
0000000c

where the first six bytes are the image header. We can see that the data from the RORG segments were relocated to >A000 and >A004, resp.

All the usual restrictions for program images apply. In particular, the first word of the first image file must be an executable instruction, and the E/A utility functions must be provided by the program.

Since the command above

$ xas99.py -R -i ashello.asm
> --- <L> **** -
***** Warning: Unresolved references: VSBW, VMBW, KSCAN, VWTR

yields a warning about unresolved VDP utility functions, we need to provide these functions ourselves, e.g., by supplying them on the command line.

$ xas99.py -R -i ashello.asm vsbw_ea.asm vmbw_ea.asm vwtr_ea.asm kscan_ea.asm

For details, please refer to the Tutorial.

Caveat: When creating an image with symbols SFIRST, SLAST and supplying utilities on the command line, e.g.,

$ xas99.py -i source.asm vsbw.asm

the code of vsbw.asm will not be included in the image, since it will be placed outside the SFIRST-SLAST range! In this case, we should use COPY.

Creating Binaries

Image files for E/A option 5 contain the actual program code that is loaded verbatim into memory. They also contain 6 bytes of metadata that instructs the loader how many files to load and where to store the data.

The binary option -b tells xas99 to generate raw binary files without metadata.

$ xas99.py -b -R -a ">6000" ascart.asm

The resulting ascart.bin file contains these bytes:

00000000  48 45 4c 4c 4f 20 43 41  52 54 21 00 03 00 00 00  |HELLO CART!.....|
00000010  02 e0 83 00 04 c0 02 01  20 00 02 02 03 00 d8 20  |........ ...... |
00000020  83 01 8c 02 02 60 40 00  d8 00 8c 02 d8 01 8c 00  |.....`@.........|
00000030  06 02 16 fc 02 00 01 8b  02 01 60 00 02 02 00 0b  |..........`.....|
00000040  d8 20 83 01 8c 02 02 60  40 00 d8 00 8c 02 d8 31  |. .....`@......1|
00000050  8c 00 06 02 16 fc 03 00  00 02 10 ff              |............|

By default, the assembler will generate one binary for the entire program. This can lead to sparse programs containing large sections of zero bytes if the source comprises non-contiguous segments. We can avoid this by using the SAVE directive described below.

The base option -a sets the base address for relocatable segments; if not set, relocatable code is kept at base 0.

Creating MAME Cartridges

The cartridge option -c tells xas99 to add a GPL header and create an RPK cartridge file suitable for the MAME emulator.

$ xas99.py -c -R ascart.asm -n "HELLO CART"

The name option -n overrides the default name of the program that shows up in the TI menu screen.

Note that the first word in the code must be an executable instruction, or we need to supply the start symbol as operand of the END directive, like was done in ascart.asm.

The resulting RPK file is a ZIP archive containing the actual program code plus various information for the MAME emulator on how to execute the program.

$ unzip -l ascart.rpk
Archive:  ascart.rpk
  Length      Date    Time    Name
---------  ---------- -----   ----
      140  02-12-2020 07:03   HELLO CART.bin
      491  02-12-2020 07:03   layout.xml
      131  02-12-2020 07:03   meta-inf.xml

xas99 will automatically generate a suitable GPL header and relocate the program to address >6030. When using AORG, make sure to leave an unused >30 byte buffer at the beginning of the program.

Note that this option is very limited in what kind of headers it can generate. We therefore recommended -c for only the simplest programs, and suggest using -b instead.

Creating Text Files

The text option -t generates a textual representation of the binary that would be generated by -b. Option -t has one parameter that specifies the format of the text. One of the following characters sets the target platform of the generated text:

Character Generated statement For use in
a DATA or BYTE assembly or GPL
b DATA BASIC
c list of values C/C++

Adding 2 or 4 to the format generates bytes or words, respectively. For target platforms with different endianness, adding r swaps the byte order in words. For example,

$ xas99.py -t a2 -R ashello.asm

yields text

;      aorg >0000
       byte >10, >0d, >48, >45, >4c, >4c, >4f, >20
       byte >57, >4f, >52, >4c, >44, >20, >20, >20
       byte >68, >69, >74, >20, >61, >6e, >79, >20
       byte >6b, >65, >79, >21, >03, >00, >00, >00
       ...

The result can be COPYed, #included, or just copy-and-pasted.

A typical use case for this option is to include a program written in language X in another program of language Y.

Embedding Code

For relocatable code not larger than around 24 KB, xas99 can generate an Extended BASIC program that invisibly contains the generated code:

$ xas99.py -R --embed-xb ascart_xb.asm

The program ascart_xb.asm is almost identical to ascart.asm, but adds the BASIC bias of >60 to each character to print on the screen.

The resulting program is a regular Extended BASIC program in so-called long format that will execute the assembly code when run. Thus, the --embed-xb options allows for the creation of assembly programs that do not require the Editor/Assembler module for execution.

The generated Extended BASIC program will have only one visible line:

$ xbas99 -p ascart_xb.iv254
1 CALL INIT :: CALL LOAD(16376,88,89,90,90,89,32,255,228):: CALL LOAD(8196,6
3,248):: CALL LINK("XYZZY")

We must not edit the generated program, though, or we will corrupt the embedded assembly code!

Creating List Files

The list option -L instructs xas99 to generate a list file for the assembled source code:

$ xas99.py -R ashello.asm -L ashello.lst

The resulting file has a similar layout to the Editor/Assembler listing:

...
0021 001C 0300  24 START  LIMI 0
     001E 0000
0022 0020 02E0  18        LWPI WRKSP
     0022 8300
0023
0024               * CLEAR SCREEN
0025
0026 0024 04C0  14        CLR  R0
0027 0026 0201  20        LI   R1,'* '
     0028 2A20
0028 002A 0202  20        LI   R2,24*32
     002C 0300
0029
...

The first columns show line number, memory address, memory contents, and timing in cycles. The memory contents may be suffixed by r for relocatable addresses and e for unknown external symbols introduced by REF.

The list file is useful for understanding the program layout in memory and the values of expressions.

The symbol option -S will append a dump of the symbol table to the listing. Relocatable symbols are marked by REL.

xas99 Assembly Language

The xas99 is a complete TMS9900 assembler with additional support for TMS9995 and F18A if option -5 or -18 is given, resp.

xas99 understands all assembler directives described in the Editor/Assembler manual and supported by the E/A loader, i.e.,

DEF REF EQU DATA BYTE TEXT BSS BES AORG RORG DORG EVEN
IDT DXOP COPY END

Note that the DORG directive is supported, even though the TI assembler does not do so.

The following directives are not supported by the E/A loader and are silently ignored by xas99:

PSEG PEND CSEG CEND DSEG DEND LOAD SREF LIST UNL PAGE TITL

xas99 also defines a number of new directives, which are described in the xdt99 Extensions section.

Includes and Filename Handling

The COPY directive is used to include an external assembly source into the current source unit.

Its filename argument may be a native path such as "~/ti99/asm/sound.asm" or "C:\TI Stuff\ASM\Sound.asm", but also a TI-style path such as DSK1.SOUND or DSK.UTILS.SOUND. In the latter case, xas99 will search for include files

SOUND
SOUND.A99
SOUND.ASM
SOUND.S

and their corresponding lower-case variants. Note that for case-sensitive platforms such as Linux, files with mixed-case filenames such as Sound.Asm will not be found when using TI paths!

xas99 searches for files in the current directory of the including file and the lib directory of the xdt99 installation. We can provide additional search paths with the include path option -I.

$ xas99.by ashello.asm -I gfx/ ../disk2/

For reasons described in the Tutorial, -I must appear after the source filename.

xdt99 Extensions

The xas99 cross-assembler offers various modern extensions to the original Editor/Assembler to improve the developer experience. All extensions are backwards compatible, so legacy source code should compile with xas99 as-is.

Comments may be included anywhere in the source code by prepending them with a semicolon ;. A semicolon inside a text literal or filename does not introduce a comment.

Source code is processed case insensitively so that all labels, expressions, and instructions may be written in upper case, lower case, or any mixture. Text literals are still case-sensitive, though.

label1 byte >A,>b
LABEL2 TEXT 'Hello World'
Label3 mov Label1(R1),Label2(r2)

Labels may be of arbitrary length and may contain arbitrary characters except for whitespace and operators (+-*/$#!@'"). Labels not imported or exported by REF or DEF, resp., may even be in Unicode. An optional colon : may be appended to the label name. The colon is not part of the name, but logically continues the current line to the next:

my_label_1:
    equ 1         ; assigns 1 to my_label_1      \
my_label_2:                                      |  xas99 behavior
    aorg >a000    ; assigns >a000 to my_label_2  /
my_label_3        ; assigns >a000 to my_label_3  \  standard E/A
    aorg >b000    ; no label to assign >b000 to  /  behavior

Local labels simplify the implementation of small loops and subroutines to be COPYed. A local label is introduced by an exclamation mark ! and an optional name. Thus, the simplest local label is just a single !. Local labels need not be unique within the program.

References to local labels are resolved relative to the current position. By default, matching labels are searched after the current position. References prefixed with a unary minus sign - are searched before the current position.

clear_data:
    li   r0, >a000
    li   r2, >100
!   clr  *r0+         ; make jump target without potential name conflicts
    dec  r2
    jne  -!           ; jump to target two lines above
    rt

Doubling, tripling, … the number of !s before a reference refers to the second, third, … match of the local label relative to the current position:

!   dec  r1              <-+
    jeq  !     --+         |
    inc  r2      |         |
    jne  !!      |  --+    |
    jmp  -!      |    |  --|
!   dec  r2    <-+    |    |
    jmp  -!!          |  --|
!   inc  r1         <-+    |
    jmp  -!!!            --+
!   rt

Note that the search for the nearest local label doesn’t wrap around the source, so

!   inc  r1
    jmp  !
    end
    

yields error Invalid local target.

Labels label and !label are entirely different and can be used without conflict in the same program. Thus, local labels used in COPYed source code cannot interfere with the main source.

The use of whitespace has been relaxed. Single spaces may be used judiciously within the operand field to increase the legibility of expressions. Two or more spaces as well as a tab character introduce the comment field.

label  data addr + len - 1  comment
       movb @addr + 2(r1), *r2+ ; comment

Technical note: It is not possible to detect the beginning of the comment field based on the current instruction, as the example

maxval equ 8 * 9 would be too big

shows. Where does the comment start, and what is the value of maxval?

The extended expression syntax supports parentheses (, ), the modulo operator %, the exponentiation operator **, and binary operators bit-and &, bit-or |, bit-xor ^, and bit-not ~ as well as binary literals introduced by :.

area    equ (xmax + 1) * (ymax + 1)
addr2   equ addr1 | >A000 & ~>001F
padding bss size % 8
binval  equ :01011010

Remember that all operators have the same precedence, i.e., an expression such as 1 + 2 * 3 - 4 & 5 evaluates as (((1 + 2) * 3) - 4) & 5. This may sound annoying, but changing the established order of evaluation would break compatibility with existing sources. To adjust the order of evaluation, parentheses are used: 1 + (2 * 3) - (4 & 5).

xas99 features a number of so-called modifiers that apply to expressions.

Many programs use byte or word constants, e.g., for MOV/MOVB or C/CB instructions, when immediate values are not available or feasible. A common problem then is to keep track of all used constants. xas99 assists the developer here by warning about unused constants (see Warnings section).

A convenient alternative is to use auto-generated constants with modifiers b# and w#. As an example,

n   equ  40
    mov  w#>ff01, @status
    socb b#2 * n + 1, r1
    cb   @keycode, b#'Q'

is equivalent to this code without modifiers:

    mov  @h_ff01, @status
    socb @b_81, r1
    cb   @keycode, @b_81
b_81:
    byte 81   ; note that 'Q' == 81 == 2*n+1
h_ff01:
    data >ff01

For a word character constant such as w#'A', a zero byte is appended to the generated byte, e.g., >4100.

The b# and w# modifiers apply to the entire expression following the modifier. Parentheses can change this behavior, but doing so will yield meaningless results. For example,

    mov (w#30) + 2, r0

is equivalent to

    mov @c_30 + 2, r0
c_30:
    data 30
    data ???

which will store an unknown value ??? in R0.

The assembler ensures that each value is added only once, so for constants b#>41, b#65, and b#'A', it will add only one constant to the code.

For each auto-generated constant, a BYTE or DATA directive will be generated. To denote where these values should be placed, the AUTO directive is used. During assembly, it will be replaced by a sequence of BYTEs and DATAs.

    save >2000,>3000

    aorg >2000
start:
    movb b#1, @acc
    ...
    auto
    ...
    aorg >2ffc
start_vector:
    data >8300
    data start

Auto-generated constants observe banks, and only appear in the bank where they were defined. You can place AUTO only in those banks, where at least one auto-generated constant is used. If on the other hand an AUTO is missing, an error is thrown.

All auto-generated constants will also appear in the list file.

The symbol size modifier s# returns the size of the label it is attached to, where size is defined as the difference of the address of the attached symbol and the address of the syntactically next symbol.

     li   r0, 320
     li   r1, text1
     li   r2, s#text1      ; s#text1 data 12
     bl   @vmbw
     ...
text1:
    text 'HELLO WORLD!'
text2:
    text 'GOOD BYE!'

In this example, s#text1 translates to the address of an automatically generated word constant 12, since the address difference of @text1 and @text2 is 12 bytes.

The size modifier detects if the last byte of the range is a padding byte and subtracts it from the size.

text1:
    text 'HELLO WORLD'    ; now 11 bytes, but 12 bytes difference
start:
    lwpi >8300

Here, s#text1 yields 11, even though there are still 12 bytes difference between @text1 and @start, as the lwpi instruction must be placed on an even address.

Keep in mind that s# requires a label immediately following the text or byte constant it refers to. In practice, this should almost always be the case.

Note that s# only applies to labels; symbols created by EQU are not supported.

The cross-bank access modifier x# enables cross-bank symbol access. For a detailed description on x#, see the paragraph on bank switching further down.

We can supply additional symbols from the command line with the define option -D.

$ xas99.py ashello.asm -D symbol1 symbol2=2

If no value is given, the symbol is set to value 1.

Symbols defined by -D are treated internally like labels and are stored as absolute address. They are not added to the DEF lists.

The symbol option -E dumps all symbols in EQU-like syntax to an external file sym.asm:

$ xas99.py -R ashello.asm -E sym.asm

The result reads like

CLS:
       equ  >002E  ; REL    <-- relocatable address
GPLST:
       equ  >837C  ;
KCODE:
       equ  >8375  ;
...

and can be COPYed into another program.

xas99 also provides new directives. The BCOPY directive includes an external binary file as a sequence of BYTEs. For example, if sprite.raw is a raw data file containing some sprite pattern

00000000  18 3c 7e ff ff 7e 3c 18                           |.<~..~<.|

then including this file with BCOPY

sprite  bcopy "sprite.raw"

is equivalent to statement

sprite  byte >18,>3c,>7e,>ff,>ff,>7e,>3c,>18

The TEXT directive also supports hex strings, e.g.,

pattern text >8040201008040201

The STRI directive is similar to TEXT, but prepends a length byte. In other words,

stri 'HELLO WORLD'

is equivalent to

text >0b, 'HELLO WORLD'

The FLOA directive stores a decimal number in the 8-byte RADIX-100 format used by the TI 99. Note that digits exceeding the accuracy of RADIX-100 are silently ignored.

floa 123.456789012

The exponent notation 1e9 is currently not supported.

The BANK directive specifies the memory bank and optionally the base address for the following code segment, or a shared code segment if the special value ALL is used. Banks count from zero.

* asbank.asm
      bank all, >6000
func1 clr r0
      ...
      bank 1
func2 li  r1,>1234
      ...

The address of a BANK directive defines the base address for other, addressless BANKs. In the previous example, bank 1 also starts at >6000, since bank 0 defined that base address.

A shared segment introduced by BANK ALL without optional address first obtains the next available addresses for all banks, and then picks the biggest one as start address. If a plain BANK n without address follows a shared segment, then its start is at the end of the shared segment.

For example, the program

Within each bank, all *ORG directives may be used, without leaving the current bank.

Note that the optional second argument of the AORG directive to specify the current bank has been removed, and is no longer available. Programs with such a directive will fail during assembly.

Generating binary files with the -b command stores banked segments in separate files. For example, assembling source file asbank.asm containing directives

BANK 0
BANK 1
BANK ALL

into a binary will yield files asbank_b0.bin and asbank_b1.bin.

xas99 detects cross-bank accesses in address arguments. Of those, accesses from and to shared code segments are fine, but others are at least dubious.

By default, xas99 allows all cross-bank accesses. Using the cross-check option -X, however, makes the assembler issues an error for each illegal cross-bank access.

So, assuming -X is supplied for the following program, only the ok accesses are legal, and the error accesses throw an error.

      bank 0, >6000
l1    b    @l3      ; ok
      b    @l2      ; error: different bank

      bank 1
l2    b    @l3      ; ok
      b    @l1      ; error: different bank

      bank all, >7000
l3    b    @l1      ; ok, could branch to bank 0 or 1, i.e., l1 or l2

Also, the B instructions in segment >7000 will branch to L1 or L2, depending on which bank is active then.

If cross-bank accesses are illegal (-X), the cross-bank modifier X# still overrides checks for individual uses, e.g., because the offending code will be relocated to a different memory address during runtime.

      bank 0
cont  clr  r0

      bank 1
      b    @x#cont  ; OK, no error

The new XORG directive sets the location counter to a new address but does not change the actual placement of the subsequent code segment.

      aorg >6000
l1    data 0             ; l1 = >6000
      bl   @func         ; branches to >8382

l2    xorg >8380         ; l2 = >6006
l3    data 0             ; l3 = >8380
func  inc  @l3
      rt
l4    aorg               ; l4 = >600C
      ...

The list file for this program shows that the code of the XORG segment is placed within the >6000 segment, but the labels get values in the >8380 range.

XAS99 CROSS-ASSEMBLER   VERSION 3.0.0
     **** ****     > t.asm
0001                     aorg >6000
0002 6000 0000     l1    data 0
0003 6002 06A0  32       bl   @func
     6004 8382
0004
0005               l2    xorg >8380
0006 6006 0000     l3    data 0
0007 6008 05A0  34 func  inc  @l3
     600A 8380
0008 600C 045B  20       rt
0009               l4    aorg
...
    FUNC................ >8382 :
    L1.................. >6000 :
    L2.................. >6006 :
    L3.................. >8380 :
    L4.................. >600E :

XORG is useful for assembling code blocks that will be moved to a different memory location, e.g., the scratchpad RAM, during run time.

* move function to scratchpad RAM
init  li   r0, >8380     ; target address for XORG segment
      li   r1, l2        ; start address of XORG segment
      li   r2, l4 - l2   ; length of XORG segment to copy
      bl   @memcpy

Note that XORG does not place code directly at the target address. Instead, we must copy all XORG segments during runtime, e.g., using the code template shown before.

The SAVE directive limits the memory range to output and controls the resulting files for the image -i and binary -b output. For those formats, each SAVE directive will yield one file, containing only code in the memory range specified.

      save >6000,>7000   ; generate single image for >6000->6fff

      aorg >6100
main  limi 0
      ...
      aorg >6800
subr  clr  r0
      ...                ; assume final address is >6DFE
      end

By default, the resulting binary will contain the entire address range of the SAVE(s), with bytes at unspecified addresses set to 0.

When supplying the minimize option -M, however, save ranges are minimized, i.e., the resulting binary only contains those addresses contained in the program (and zero any gaps between them).

As an example, the simple program

     save >2000, >2100
     aorg >2010
     data 1, 2, 3, 4

will contain >100 bytes normally, but only 8 bytes together with -M.

Note that always the entire program is assembled, even if only a portion of it is SAVEed.

In combination with banking, there will be one output file per SAVE per bank, even if that file is empty.

The arguments of SAVE may be expressions, and may be omitted to denote the start and end of a program, resp.

      save lab1, lab2 + >100
      save ,>5000
      save >6000,

If no SAVE directives are provided, option -b will create one binary file for the entire program. Option -i will save the region between symbols SFIRST and SLAST, if present, and generate one file for each segment otherwise.

The source code preprocessor allows for conditional assembly based on well-defined conditional expressions. The preprocessor commands .ifdef and .ifndef check if a given symbol is defined or not.

       .ifdef lang_de
msg    text 'Hallo Welt'
       .else
msg    text 'Hello World'
       .endif

The commands .ifeq, .ifne, .ifgt, and .ifge test if two arguments are equal, not equal, greater than, or greater than or equal, resp. If the second argument is missing, the first argument is compared against value 0.

Conditional assembly preprocessor commands may be nested. Valid conditional expressions and their rules of evaluation correspond to those of the EQU directive.

The .print preprocessor command prints its arguments to stdout.

answer equ 42
       ...
       .print 'Selected answer is', answer

The .error command prints a message to stderr and aborts the assembly.

       aorg >6000
       ...
       .ifgt $, >7fff
       .error 'Cartridge program too large'
       .endif

In addition to symbols defined by labels, xas99 also sets exactly one of

_xas99_obj
_xas99_image
_xas99_bin
_xas99_cart
_xas99_xb 

depending on the assembler mode selected. We can use these symbols to enable the generation of multiple formats from one source.

xas99 supports macros. The .defm preprocessor command introduces a new macro, which is terminated by the .endm command. Inside the macro body, the macro parameters #1, #2, … are substituted by the macro arguments when instantiating the macro:

* fill bottom #1 rows with char #2
    .defm fill
    li   r0, 768
    li   r1, #2
    li   r2, #1 * 32
    s    r2, r0
    bl   @vmbw
    .endm

Macro parameters may only occur in operand positions, but not in labels or mnemonics. Parameters in literals, e.g., text '#1', are also not substituted. These restrictions currently prevent advanced macro trickery.

Macros are used like preprocessor commands, with any arguments separated by commas:

    .fill 10, '* '

Macro instantiations are parsed like normal instructions, so macro arguments cannot contain certain symbols such as , or ;. Empty arguments are allowed if the macro expects at least two parameters.

Macro parameters are resolved by textual replacement. Thus, when a macro containing the line

    li   r0, 2 * #1

is instantiated with argument 1 + 2, the resulting code will assign R0 the value 4 instead of 6. We can avoid these pitfalls by supplying expressions in parentheses:

    .macro (1 + 2)

Labels are allowed inside macro definitions. To avoid duplicate symbols when instantiating a macro more than once, all labels should be local.

A macro can instantiate other macros, but instantiations must not be circular. Macro definitions cannot be nested.

Preprocessor commands are always executed, even inside inactive .ifdef/ .endif blocks. The correct way to define environment-dependent macros is thus

.defm mymacro
.ifdef symbol
clr r0
.else
clr r1
.endif
.endm

instead of using .defm.endm inside .ifdef.endif.

xas99 also supports TMS9995 opcodes

MPYS <gas>
DIVS <gas>
LWP  <wa>
LST  <wa>

when using the -5 option, and the F18A GPU instruction set

CALL <gas>
RET
PUSH <gas>
POP  <gad>
SLC  <wa>, <count>
PIX  <gas>, <wa>

when using the -18 option. The SPI family of instructions is not supported; please use their equivalents CKON, … instead.

Linker

xas99 features a linker that can join object code files into any supported format. The linker is invoked by link option -l or by supplying more than one source file.

If fileN.obj is the object code of source file fileN.asm, then these commands are equivalent and yield the same file result.obj:

$ xas99.py file1.asm file2.asm file3.asm ... -o result.obj
$ xas99.py file1.asm file2.asm -l file3.obj ... -o result.obj
$ xas99.py file1.asm -l file2.obj file3.obj ... -o result.obj
$ xas99.py -l file1.obj file2.obj file3.obj ... -o result.obj

The order is important, though, so

$ xas99.py file2.asm -l file1.obj file3.obj ... -o result.obj

will yield a different result.

Note that for the Editor/Assembler cartridge, the option 3 loader assumes the role of the linker.

Linking will determine a memory layout for all object code files, and match symbols imported by REF with symbols exported by DEF. Linking mostly concerns relocatable code, since the position of absolute code is fixed.

As an example, linking (the object code of) files

    def x2
    rorg >10
x1  data 1
x2  data 2
    aorg >20
x3  data x2

and

    ref x2
    rorg >20
y1  data 4
    aorg >22
y2  data 5

yields this file (ignoring the order of instructions, but not their addresses):

    rorg >10
    data 1
    data 2
    rorg >34       ; next available reloc addr >14 + RORG offset >20
    data 4
    aorg >20
    data >12
    data 5

The xas99 linker has two modes. The default mode follows the logic of the E/A loader. The safe mode, invoked by safe link option -ll, additionally resolves conflicts that may arise when linking relocatable code with absolute code. As an example, linking

    * program 1
    rorg >a000
    data 1
    aorg >a010
    data 2, 3

    * program 2
    rorg >10
    data 4
    

creates a conflict at address >A012, since both DATA 3 and DATA 4 will be placed at that address. (Note that for program 2, the next available relocatable address is >A002, and the RORG offset is >10.)

Option -l will not resolve this conflict, and the later instruction DATA 4 will be placed at >A012. Option -ll, on the other hand, resolves the conflict by moving the conflicting program unit towards higher addresses until all conflicts are resolved. In this example, DATA 4 is placed at >A014.

When finding a layout, with or without conflict resolution, each individual object code file is placed as a unit, i.e., the same positive offset is applied to all relocatable segments of one program unit.

Safe linking is most useful when linking source or object code that someone else has written and which may contain unknown conflicts. When linking our own program, normal linking should be sufficient.

Compatibility with E/A

The strictness option -s disables most xas99-specific extensions, in particular the relaxed syntax, to improve backwards compatibility for legacy sources:

$ xas99.py -s ashello.asm

Strictness is required, for example, to assemble the Tombstone City sample source shipped with the Editor/Assembler package, as some comments in Tombstone do not adhere to the two-space separator rule of xas99.

R5LB   EQU SUBWS+11 * REGISTER 5 LOW BYTE.
***** Unknown symbol: REGISTER 5 LOW BYTE.

Finally, note that case insensitivity cannot be disabled.

xga99 GPL Cross-Assembler

The xga99 GPL cross-assembler translates programs written in TI’s proprietary Graphics Programming Language into byte code that can be interpreted by the TI 99 home computer.

Invoking xga99 in standard mode will assemble a GPL source code file into GPL byte code that may be placed in a physical or emulated GROM or GRAM device.

$ xga99.py gahello.gpl
$ xga99.py gahello.gpl -o HELLOG

The output parameter -o may be used to override the default output filename using extension .gbc (for “GPL byte code”).

Note that in gahello.asm, the GROM directive is commented out, which places the byte code in GROM 0 by default. We can override this with the GROM option -G. For example, to place the byte code in the cartridge GROM,

$ xga99.py gahello.gpl -G ">6000"

By default, xga99 will yield one single file for the entire program, even if it spans multiple GROMs. To generate one file per GROM, we can use the split GROM option -g.

$ xga99.py sample.gpl -g

Note that -g splits based on GROM directives, and not by size. Therefore, we must ensure ourselves that the size of each GROM does not exceed >2000 bytes.

The cartridge parameter -c relocates the GPL program to the cartridge GROM area, generates GPL header data, and packages the byte code image into a cartridge file suitable for the MAME emulator.

$ xga99.py -c gahello.gpl

The resulting .rpk file may be executed as-is by the MAME emulator:

$ mame64 ti99_4a -cart gahello.rpk

The name parameter -n overrides the default name of the program that shows up in the TI 99 menu selection screen.

$ xga99.py -c gahello.gpl -n "HELLO GPL WORLD"

Again, we recommend -c only for very simple programs, and suggest using plain byte code instead.

The text option -t creates a textual representation of the byte code. The text format can be specified similarly to xas99.

$ xga99.py -t b4 gahello.gpl -o -
DATA -1, -1, -1, -1
DATA 0, 0, 0, 0
DATA -1, -1, -1, -1
DATA 13382, 27309, -9019, 24291
DATA 13382, 27309, -9019, 24291
...

The listing option -L creates a list file that shows the addresses and byte values for each source line.

$ xga99.py gahello.gpl -L gahello.lst

When -L is given, the symbol dump option -S includes the symbol table in the list file.

The include path option -I, the define option -D, the quiet option -q and the symbol dump option -E work identical to their xas99 counterparts.

As the Graphics Programming Language was never intended for public release, existing tools for assembling GPL source code differ substantially in the syntax they use. xga99 adopts a combination of the Ryte Data and the RAG GPL Assemblers’ syntax as its native format.

We can choose other syntax styles, however, with the syntax parameter -y. Currently, the only extra syntax is the syntax of the TI Image Tool disassembler, available with name mizapf (named after the creator of the image tool).

$ xga99.py gahello_timt.gpl -y mizapf

Note that the original GPL syntax described in TI’s GPL Programmer’s Guide is considered too arcane to be included in xga99.

The native xga99 syntax style is more “modern” in that it supports lower case sources, extended expressions, relaxed labels, local labels, and relaxed use of whitespace, similar to xas99. Both cross-assemblers also share the same preprocessor.

GPL Instructions

xga99 supports all GPL mnemonics described in the GPL Programmer’s Guide, but adopted the common reversed operand order Gs, Gd for all but the shift instructions.

Operands use the following prefix notation for (CPU) RAM, VDP RAM, and GROM addresses, resp.:

Prefix To address type Yields Restrictions
@ RAM RAM direct
* RAM RAM indirect
V@ VDP RAM VDP RAM direct
V* RAM (!) VDP RAM indirect
G@ GROM GROM/GRAM direct MOVE only
@ (@) RAM (Pad RAM) CPU RAM indexed
V@ (@) VDP RAM (Pad RAM) VDP RAM indexed
G@ (@) GROM (Pad RAM) GROM/GRAM indexed MOVE only
# VDP register VDP register MOVE only

Note that indexes must be located in scratchpad RAM. We can thus abbreviate an indexed address like V@>100(@>83e0) to V@>100(@>e0).

There is no G*<RAM> GROM indirect address mode, but G0(<Pad RAM>) can be used for Scratchpad RAM addresses instead.

Labels, even when attached to instructions, do not represent any memory type. We could thus use any address prefix on any label, which on the other hand implies that we must use G@ in MOVE instructions:

t1  text 'HELLO'
    move 5, g@t1, v@100

The only exceptions to this rule are branch and call instructions, where the address prefix G@ is optional:

    b    l1
    b    g@l1

And just as we can tag labels in expressions with any address prefix, we cannot endow a label with a type:

s   equ  v@1    ;  Error: Unknown symbol: V@1

Expressions are built using arithmetical operators +, -, *, /, %, and ** and bit operators &, |, ^, and ~. Expressions are evaluated left-to-right with equal operator precedence; parentheses may be used to change the order of evaluation. For further details, please refer to the xas99 section on expressions.

Literals may be decimal numbers, hexadecimal numbers prefixed by >, binary numbers prefixed by :, and text literals enclosed in single quotes '.

byte 10, >10, :10, '1'

The following mnemonics for the FMT sub-language are recommended, but the styles of Ryte Data and RAG are also available. Finally, we can choose other styles with the -y option.

HTEXT/VTEXT <text>
HCHAR/VCHAR <count>, <char>
HSTR <count>, <addr>          (no GROM, no VDP, no indexing, no indirection)
ROW/COL <count>
ROW+/COL+ <count>
BIAS <count/gs>
FOR <count> ... FEND [<label>]

Here, <count> represents an immediate value.

GPL Directives

The xga99 GPL assembler supports the following directives:

GROM AORG EQU DATA BYTE TEXT STRI FLOAT BSS TITLE COPY BCOPY

Directives affecting listing generation are currently ignored:

PAGE LIST UNL LISTM UNLM

Most xga99 directives work very similar to their xas99 counterparts.

The BYTE and DATA directives insert bytes and words into the program, resp., irrespective of the size of their arguments.

label byte 1, >02, :11011010, '@', >100     ; >100 becomes >00
      data 1, >1000, 'A'                    ; 'A' becomes >0041

The TEXT directive generates a sequence of bytes from a text literal or an extended hexadecimal literal.

label text 'Groovin'' With GPL'
      text >183c7effe7c38100

Note that the second instruction is equivalent to BYTE >18,>3C,>7E,....

The STRI directive works similar to the TEXT directive, but prepends a length byte to the generated byte sequence.

The FLOAT directive stores a decimal number in the 8-byte RADIX-100 format used by the TI 99. Note that digits exceeding the accuracy of RADIX-100 are silently ignored.

float -123.456789012

The exponent notation 1e9 is currently not supported.

The GROM directive sets the GROM base address for the code that follows. You can specify either the GROM number 0, …, 7, or the absolute address >0000, …, >e000, where bits 0-12 are ignored.

If more than one GROM directive is placed in one program, each GROM segment will be placed in a separate file, whose name is appended with the GROM address.

The AORG directive is used to place individual code segments at specific addresses within the given GROM. The address argument is thus relative to the GROM base address given by GROM.

Instead of using the GROM and AORG directives, the location of the byte code may also be specified by the GROM option -G and AORG option -A, resp. The cartridge option -c implies -G 0x6000 and -A 0x30.

Options -G and -A will not override GROM or AORG directives, but set the GROM and address offset of the first line of the code.

The COPY and BCOPY directives include text files or binary files, resp. A binary file is translated as a sequence of BYTEs.

xdt99 Extensions

The xga99 GPL cross-assembler offers various “modern” extensions to the original TI GPL specification to improve the developer experience. All extensions are backwards compatible so that any existing source code using suitable syntax should assemble as-is.

The xas99 extensions regarding comments, labels, local labels, whitespace, expressions, external symbols and the preprocessor also apply to xga99. Note, however, that GPL macros use macro parameters $1, $2, … instead of #1, #2, …, as the # sign is used to denote VDP registers in GPL.

The predefined symbols set by xga99 are _xga99_gbc or _xga99_cart, depending on the output format chosen.

xda99 Disassembler

The cross-disassembler xda99 is a command-line tool to convert machine code back into assembly source code.

As an example file for this section, we will use ascart.bin, among others, which we can create by typing

$ xas99.py -R -b ascart.asm

To disassemble a binary machine code file, we need to tell the disassembler the first address of the machine code with address option -a and the starting address for the disassembly with “from” option -f:

$ xda99.py ascart.bin -a 6000 -f 600c

All command line values are interpreted as hexadecimal values. They can optionally be prefixed by > or 0x.

The resulting file ascart.dis contains the disassembled instructions in a listing-like format:

            aorg >6000
6000 4845?
6002 4c4c?
6004 4f20?
6006 4341?
6008 5254?
600a 2100?
600c 0300   limi  >0000
600e 0000
6010 02e0   lwpi  pad
6012 8300
6014 04c0   clr   r0
...

We see for each addresses the contents and the assembly instruction located at the address. Words showing ? have not been disassembled.

The output option -o redirects the output to a different file, or prints to stdout when using the special filename -.

We can also specify an upper bound on the range to disassemble with the “to” option -t.

By default, xda99 disassembles TMS9900 machine code. We can, however, extend the recognized opcodes to TMS9995 and F18A by supplying options -5 or -18, resp.

The skip option -k skips some bytes at the beginning of the binary to disassemble. For example, when disassembling an E/A option 5 image, we use -k to skip the 6-byte header:

$ xda99.py ashello5.img -k 6 -a a000 -f a000

Machine code consists of both code and data segments, which are often intermingled. Without context information, however, a disassembler cannot tell data from code.

Using xda99 with the from parameter -f will start the disassembly in top-down mode, which disassembles sequentially word by word. This mode often yields bad results, as data segments will be translated into meaningless statements.

For example, if we change the from address in the ascart.bin example above to -f 6000, we get

$ xda99.py ascart.bin -a 6000 -f 6000 -o -
            aorg >6000
6000 4845   szc   r5, @>4c4c(r1)     |
6002 4c4c                            |  data erroneously
6004 4f20   szc   @>4341, *r12+      |  disassembled into
6006 4341                            |  source code
6008 5254   szcb  *r4, r9            |
600a 2100   coc   r0, r4             |
600c 0300   limi  >0000
600e 0000
...

For some kinds of data, we can spot if the data was disassembled erroneously, as the resulting source often contains uncommon mnemonics and operands with complex address formats and random-looking addresses.

The situation gets worse when disassembling data into nonsense statements spills over to the real code, e.g., if the last data word is assembled into a two-word instruction:

    aorg >a000
    byte 4, 224
start:
    lwpi >8300
    limi 0
    ...

Disassembling the machine code generated by above program with -f a000 yields

            aorg >a000
a000 04e0   clr  @>02e0        |  disassembled data
a002 02e0                      |  swallowed the LWPI
a004 8300   c    r0, r12       |  instruction
a006 0300   limi >0000
a008 0000
...

If the data segments are known, those can be excluded from disassembly with the exclude option -e.

$ xda99.py ascart.bin -a 6000 -f 6000 -e 6000-600c

The upper address yyyy of an exclude range xxxx-yyyy is not included in the range, so range 6000-6000 is an empty range. Range addresses should always be even.

For unknown programs, excluding data segments is difficult. Thus, xda99 offers an additional run mode -r that observes static branch, call, and return statements, and disassembles only along the program flow.

$ xda99.py ascart.bin -a 6000 -r 600c

For the ascart.bin program, though, there is no difference between run mode and top-down mode, as code and data are separate in that program.

Run mode is not limited to one starting address:

$ xda99.py suprdupC.bin -a 6000 -r 6034 603c

For convenience, the special run start address start denotes all start addresses derived from the machine code. Thus, the above line becomes

$ xda99.py suprdupC.bin -a 6000 -r start

Currently, start only works for cartridge images containing a GPL header. In all other cases, start defaults to the address given by -a.

Run mode adds jump marker comments to the output that show from which address a given instruction was branched to:

6058 d809   movb r9, @>837c
605a 837c
605c d809   movb r9, @>8374           ; <- >6068
605e 8374
6060 0420   blwp @kscan
6062 2108
6064 9220   cb   @>8375, r8
6066 8375
6068 13f9   jeq  >605c
606a d020   movb @>8375, r0
606c 8375

The program option -p turns the disassembly into actual source code that can be re-assembled again:

       aorg >6000
vdpwd  equ  >8c00
pad    equ  >8300
gpllnk equ  >2100
vdpwa  equ  >8c02
l6000  data >4845
l6002  data >4c4c
l6004  data >4f20
l6006  data >4341
l6008  data >5254
l600a  data gpllnk
l600c  limi >0000
l600e
l6010  lwpi pad
l6012
l6014  clr  r0
...

The -p options will also include an EQU stanza of all symbols used, in this case all xas99 internal symbols that were imported with REF by the program.

To use more symbols, a symbol file can be supplied with the -S parameter. The symbol file can be generated with the EQU option -E of xas99, or written manually in a fairly free style, e.g.,

s1 equ >10
s2:
        equ 10
s3 >10
s4: 0x10

Data segments often contain strings, that can be restored heuristically by using the string option -n, either with or without the -p option.

$ xda99.py ascart.bin -a 6000 -f 600c -n -o -
            aorg >6000
6000 4845   text  'HELLO CART'
6002 4c4c
6004 4f20
6006 4341
6008 5254
600a 2100?
600c 0300   limi  >0000
600e 0000
6010 02e0   lwpi  pad
...

Option -n tries to find strings in un-disassembled areas. Thus, -n is only useful in run mode or top-down mode with exclusions, as otherwise top-down mode will not leave behind any data segments where strings could be found.

Note that currently, xda99 only disassembles even length strings.

The concise option -c ignores all non-disassembled addresses in the output by merging those addresses marked by ? and replacing them by .....

            aorg >2000
2000 1008   jmp  >2012
....
2012 c481   mov  r1, *r2
2014 05a2   inc  @>0002(r2)
2016 0002
2018 2881   xor  r1, r2
201a 1309   jeq  >202e
201c 10fa   jmp  >2012

Options -c and -p cannot be combined.

The strict option -s generates output files in legacy Editor/Assembler format, in particular in upper-case and without extra whitespace.

The register option -R tells the disassembler to use plain integers for registers, i.e., to not prepend registers with R.

Run Mode and Conflicts

When the run mode disassembler hits an address which has already been disassembled, it stops the current run. This regularly happens for multiple calls to a subroutine, loops, or recursion, and is perfectly normal.

But run mode is not always 100% accurate, as xda99 cannot follow indirect branches such as B *R1, and doesn’t know if a condition for JEQ LABEL is always true and thus has no alternate path. (The latter remark is more relevant for xdg99, where BR is often used as a shorter B.) As a consequence, a run may “run off”, and worse, different runs may try to disassemble the same range differently:

               First run,              Second run,
               starting @>6000         starting @>6002

               aorg >6000              aorg >6000
6000 c820      mov  @pad, @>831c                         |
6002 8300                              c    r0, r12      | disagreement
6004 831c                              c    *r12, r12    |
6006 0a51      sla  r1, 5              sla  r1, 5
6008 1620      jne  >604a              jne  >604a

Above, the second run hits an address that is only part of a previously disassembled address (i.e., an operator), which raises a conflict about which version is correct.

The default behavior of xda99 is to stop the run, leaving the previous disassembly untouched. You can override the default with the force option -F, which will always overwrite previous results. This is done cleanly, so that run 2 above will reset the overridden instruction at address @>6000.

There is no recommendation to disassemble with or without force. The result of each disassembly may vary with each binary, and should be tried out.

In general, we should not expect an optimal result by invoking xda99 just once. Instead, disassembly is an iterative process, where the run mode will continuously uncover new code fragments, and where previous disassemblies have to be revised as we gather new information about the program.

xdg99 GPL Disassembler

The GPL disassembler xdg99 is a command-line tool to translate GPL byte code into GPL source code.

xdg99 shares almost all options with xda99, and works very similar. In fact, at some point in the future, both programs might be merged into one.

To show the similarities,

$ xdg99.py gacart.gbc -a 6000 -f 6030

disassembles byte code file gacart.bin, into GPL instructions:

          grom >6000
          aorg >0000
6000 aa?
...
602f 00?
6030 07   all   >20
6031 20
6032 04   back  >04
6033 04
6034 be   st    >48, v@>0021
6035 a0
6036 21
6037 48
...

The only option that xdg99 features over xda99 is the syntax selection option -y, which is already known from xga99:

$ xdg99.py gacart.bin -a 6000 -f 6030
...
6206 31   move >0010, g@>6ec4, v@>0033
...

$ xdg99.py gacart.bin -a 6000 -f 6030 -y mizapf
...
6206 31   move >0010 bytes from grom@>6ec4 to vdp@>0033
...

At the same time, the -R option of xda99 has no meaning for GPL, and thus is not supported by xdg99.

xbas99 TI BASIC and TI Extended BASIC Tool

xbas99 is a command-line tool for converting TI BASIC and TI Extended BASIC programs from source format to internal format, and vice versa. For brevity, we will refer to both TI BASIC and TI Extended BASIC programs simply as BASIC programs.

Programs in source or listing format are plain text files that contain the BASIC statements that a user would type in. These kind of text files are usually not stored on a floppy disk.

Programs in internal or tokenized format are TI-specific files in PROGRAM format that are generated by the SAVE command and understood by the OLD and RUN commands. xbas99 also supports programs created in so-called long format of file type INT/VAR 254 and merge format of type DIS/VAR 163.

Typical use cases for xbas99 include the listing of programs stored in internal format and the creation of program files for the BASIC interpreter from a text file with BASIC statements.

The create option -c encodes a BASIC listing into internal format so that the resulting file can be loaded and run by one of the BASIC interpreters.

$ xbas99.py -c bashello.bas

xbas99 uses the .prg extension for BASIC programs in tokenized format.

The print option -p lists the statements of a BASIC program in tokenized format on the screen. Formatting is identical to the built-in BASIC LIST command modulo the line wrapping.

$ xbas99.py -p bashello.prg
10 REM HELLO
20 INPUT "YOUR NAME? ":NAME$
30 PRINT "HELLO ";NAME$
40 END

The similar decode option -d saves the listing of program to a file.

$ xbas99.py -d bashello.prg -o bashello2.bas

BASIC programs in long format are detected automatically. To list programs in merge format, we must add the merge option --merge. Merge format is currently not detected automatically.

The create option -c assumes that each line of the text file contains exactly one line of the program. If the listing has been formatted with a fixed line width, e.g., when stored as DIS/VAR, or derived from a physical print-out by OCR, this assumption may not hold.

To join split lines, we can use the join option -j. However, this task is not as simple as it seems, as this example in DIS/VAR 40 shows:

100 CALL CLEAR :: CALL SCREEN(2) :: CALL
 HCHAR(1,1,42,768)
110 SHIPS=3 :: SCORE=0 :: LEVEL=1 :: SHI
ELD=0 :: ALIENS=99
120 CALL KEY(0,KEY,STA):: IF KEY=9 THEN
290 ELSE GOSUB 560
130 CALL CHAR(96,"8040201008040201")
... 

As we see, program line 120 is split in two rows, and the THEN target of the IF-THEN-ELSE statement happens to be wrapped to the start of the second row. Since xbas99 does not perform a syntactic analysis, the program cannot tell if the line starting with 290 is the continuation of the previous line or the next program line with line number 290.

To handle this situation, -j has an optional parameter. This parameter tells xbas99 how many text lines each program lines may occupy, and/or what the biggest difference between two consecutive line numbers is. In the example above, the first value would be 2, because we have no program line wrapped over three or more text lines, and the second value would be 10, since the difference between two consecutive line numbers is always 10.

Thus, we should tokenize our program with

$ xbas99.py -c aliens.bas -j 2,10

If we want to provide only one of these values, we can write 2, or ,10.

Since the biggest line number difference is 10, xbas99 knows that for the line starting with 290, the 290 cannot be a line number, and thus the line must be part of the statement starting with 120.

There are additional heuristics that xbas99 applies, e.g., that line numbers must always increase. If a translation using -j fails, we need to join the lines manually.

To check that the translation was successful, we can print the listing of the tokenized program.

$ xbas99.py -p aliens.prg
100 CALL CLEAR :: CALL SCREEN(2):: CALL HCHAR(1,1,42,768)
110 SHIPS=3 :: SCORE=0 :: LEVEL=1 :: SHIELD=0 :: ALIENS=99
120 CALL KEY(0,KEY,STA):: IF KEY=9 THEN 290 ELSE GOSUB 560
130 CALL CHAR(96,"8040201008040201")
...

xbas99 also supports a label mode in which no line numbers are used. Instead, targets for branch statements such as GOTO or THEN are defined by labels.

A label has to start at the beginning of the line and must end in a colon. Other lines must be indented by at least one blank.

START:
  INPUT "CHECK WHICH NUMBER? ":N
  GOSUB @ISPRIME
  IF PRIME THEN @PRIME
  PRINT "NOT PRIME"
  GOTO @START
PRIME:
  PRINT "PRIME!"
  GOTO @START
ISPRIME:
  REM CHECK IF N IS PRIME
  ...
  PRIME=0
  ...
  PRIME=1
  RETURN

To tokenize a label-based program, we use the label option -l.

$ xbas99.py -c -l prime.bas

Note that -c will convert label-based programs into regular line number-based programs, so decoding -d will never yield a label-based program.

$ xbas99.py -p prime.prg
100 INPUT "CHECK WHICH NUMBER? ":N
110 GOSUB 170
120 IF PRIME THEN 150
130 PRINT "NOT PRIME"
140 GOTO 100
...

The long option -L instructs xbas99 to create the program in long format. Long programs are stored within the 32 KB memory expansion and may be larger than conventional programs. The creation of programs in merge format is currently not supported.

The protection option --protect will add list protection to the generated program. Programs with list protection cannot be listed or edited by the BASIC interpreters. Note, however, that the print option -p of xbas99 will not honor the protection flag.

Running BASIC Programs

Before we can run programs created by xbas99 in an emulator or on a real TI, we have to transfer them to a disk image or convert them into TIFILES format using xdm99.

$ xdm99.py -X sssd basic.dsk -a bashello.prg
$ xdm99.py -T bashello.prg -o BASHELLO

Advanced users of xdt99 may also combine the creation of the BASIC program file and the transfer to a disk image into one single step using a pipe:

$ xbas99.py -c bashello.bas -o - | xdm99.py basic.dsk -a - -n HELLO

All tools in xdt99 follow the convention that the special filename - denotes stdin or stdout, depending on context. We can also pipe from xdm99 into xbas99 to list BASIC programs that are stored on a disk image:

$ xdm99.py basic.dsk -p BASHELLO | xbas99.py -p -
10 REM HELLO
20 INPUT "YOUR NAME? ":NAME$
30 PRINT "HELLO ";NAME$
40 END

Also note that xbas99 will read and encode any text file that we supply, with only minimal syntax checking. In other words, the resulting program file should always load with OLD, but it may not RUN. A future version of xbas99 may contain more advanced syntax checks to assure that only correct programs may be tokenized.

xdm99 Disk Manager

xdm99 is a command-line tool for handling sector-based TI disk images and files in TIFILES or v9t9 format.

Cataloging Disks

When we invoke xdm99 without any options, the tool prints the file catalog of the disk image to stdout:

$ xdm99.py ed-asm.dsk
ED-ASSM   :     97 used  263 free   90 KB  1S/1D  40 TpS
----------------------------------------------------------------------------
ASSM1         33  PROGRAM       8192 B            P
ASSM2         18  PROGRAM       4102 B            P
EDIT1         25  PROGRAM       5894 B            P
SAVE          13  DIS/FIX 80    3072 B   36 recs  P
SFIRST/O       3  DIS/FIX 80     512 B    5 recs  P
SLAST/O        3  DIS/FIX 80     512 B    4 recs  P

The top line shows the name of the disk, protection status, the number of used and free sectors, and the disk geometry. For each file, the number of used sectors, the file type, the file length, the number of records, and the protection status is shown. If present, the file creation or modification time is also shown.

xdm99 warns about any inconsistencies it may find, e.g., blocks claimed by files that are not allocated in the allocation map. For example, when using the Editor/Assembler on a real machine with the TI Floppy Disk Controller, these inconsistencies happen more frequently than one would assume. Files affected are flagged with ERR in the catalog. In such cases, we can use the repair option -R to automatically try to repair disks with inconsistencies.

Extracting Files

The extract option -e extracts one or more files from the disk image to the local file system.

$ xdm99.py work.dsk -e HELLO-S CART-S

The local filename is derived automatically from the TI filename by lowercasing. If we want to keep the original filename as it was on the disk, we can use the TI-style name option -N.

We can override the default name with the output option -o.

$ xdm99.py work.dsk -e HELLO-S -o hello.asm

If -o specifies a directory, all output files are placed in that directory.

$ xdm99.py work.dsk -e HELLO-O HELLO-S -o ti-stuff/

When extracting two or more files, -o may only be used with a directory argument.

To print the contents of a file to stdout, the print option -p may be used.

$ xdm99.py work.dsk -p HELLO-S

In general, printing files only makes sense for files in DIS/FIX or DIS/VAR format. For INT or PROGRAM files, however, we can pipe the output of xdm99 into an external tool, e.g., hexdump, to visualize the contents.

$ xdm99.py work.dsk -p ASHELLO5 | hexdump -C
> (only possible with external hexdump utility)
00000000  00 00 00 f8 a0 00 10 0d  48 45 4c 4c 4f 20 57 4f  |........HELLO WO|
00000010  52 4c 44 20 20 20 68 69  74 20 61 6e 79 20 6b 65  |RLD   hit any ke|
00000020  79 21 03 00 00 00 02 e0  83 00 04 c0 02 01 2a 20  |y!............* |
00000030  02 02 03 00 04 20 a0 7e  05 80 06 02 16 fb 02 00  |..... .~........|
...
000000e0  a0 dc 02 e0 83 e0 c8 0b  20 aa 06 a0 00 0e 02 e0  |........ .......|
000000f0  20 94 c8 0b 83 f6 03 80                           | .......|

Note that -p is equivalent to combining parameters -e and -o -.

Filenames given by -e may be glob patterns containing wildcards * and ?. This will extract all files matching the given pattern.

$ xdm99.py work.dsk -e "H?LLO-*"

Note that on Linux and macOS platforms, we have to quote our glob pattern to prevent the shell from expanding the pattern prematurely.

Extracting files will yield the file contents only. In we also want to retain the metadata, i.e., file type and record length, we should extract files in TIFILES or v9t9 format, described below.

Working with Disks

The add option -a adds local files to the disk image. xdm99 will infer a suitable TI filename from the local filename unless an explicit filename is given by the name option -n. If the file is not of type PROGRAM, we must provide the file type using the file type option -f.

$ xdm99.py work.dsk -a ashello.asm -n HELLO-S -f DIS/VAR80

The syntax for -f is fairly permissible, e.g., DIS/FIX 80, DISFIX80, or df80 all work.

If we add multiple files with -a and specify a name with -n, all files will get that filename, but with the last character incremented for each file.

$ xdm99.py work.dsk -a intro main appendix -n NAME

will add the three files as NAME, NAMF, and NAMG to the disk image.

The rename option -r renames one or more files on the disk.

$ xdm99.py work.dsk -r HELLO-S:HELLO/S

For each file to rename, we have to provide the old and the new filename, separated by a colon :.

To rename the disk itself, we use the -n option without -e or -a options.

$ xdm99.py work.dsk -n WORK-2

The delete parameter -d deletes one or more files from the disk.

$ xdm99.py work.dsk -d HELLO-I HELLO-O
$ xdm99.py work.dsk -d "*-O"

Note that the deletion is “secure” in the sense that the contents of the deleted files cannot be found anywhere on the disk after the deletion.

The write protection parameter -w toggles the current protection status of the given files.

$ xdm99.py work.dsk -w HELLO HELLO-CPY

Note that file protection affects only TI 99 systems and emulators, and will be ignored by xdm99.

Modifying file operations, such as -a, -r, or -d, do not retain the overall sector structure of the disk. In particular, for all such operations, the disk image will be automatically defragmented. Simply cataloging the disk or extracting a file, however, will not modify the disk image.

By default, all modifying disk operations will change the disk image directly. To create an independent copy of the original disk image with the changes applied, the -o option may be used.

$ xdm99.py work.dsk -a file -o copy.dsk

The original disk image work.dsk will not be changed.

Working with Files

As we already mentioned, extracting files from a disk image to the local file system will lose certain TI-specific information, such as the file type or the record length. In order to retain this meta information, the v9t9 and TIFILES formats were created.

Both formats use a header of 128 bytes containing filename and file properties. For example, for file ASHELLO in DIS/FIX 80 format, the TIFILES header contains

$ xdm99.py work.dsk -e ASHELLO -t | hexdump -C
00000000  07 54 49 46 49 4c 45 53  00 03 00 03 a0 50 08 00  |.TIFILES.....P..|
00000010  41 53 48 45 4c 4c 4f 20  20 20 00 00 00 00 6e b9  |ASHELLO   ....n.|
00000020  28 7b 6e b9 28 7b ff ff  20 20 20 20 20 20 20 20  |({n.({..        |
00000030  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
...

and the v9t9 header contains

00000000  41 53 48 45 4c 4c 4f 20  20 20 00 00 00 03 00 03  |ASHELLO   ......|
00000010  a0 50 08 00 6e d7 28 7b  6e d7 28 7b 00 00 00 00  |.P..n.({n.({....|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
...

xdm99 supports both TIFILES and v9t9 formats by adding the TIFILES option -t or the v9t9 option -9 options to add or extract operations.

$ xdm99.py work.disk -t -e HELLO-S
$ xdm99.py work.disk -9 -e HELLO-S

By default, files extracted in TIFILES or v9t9 format will have extension .tfi or .v9t9, resp.

$ xdm99.py work.disk -t -a hello-s.tfi
$ xdm99.py work.disk -9 -a hello-s.v9t9

Note that xdm99 will not infer the format automatically, so if we forget to supply -t or -9 when adding files, the metadata of the files will be stored on the disk image as part of the file contents.

Since TIFILES and v9t9 formats already store all metadata, options -n and -f are ignored when used in combination with -t or -9.

We should note that xdm99 also handles short TIFILES files as used by Classic 99 and other programs. Short TIFILES files do not store the TI filename and creation date, but use the host filesystem information instead.

Extracted TIFILES files are always in long format. Classic 99 will use long files, but ignore the stored filename. Thus, for Classic 99, we should set the actual filename to a TI-style filename. We can easily do this with the TI-style name option -N when extracting files with -t and -e.

$ xdm99.py work.disk -t -N -e HELLO-O

Note that for v9t9 or long TIFILES files, there is no relation between the TI filename stored in the TIFILES or v9t9 metadata, and the host filename of the TIFILES or v9t9 file itself. Renaming the file will not change the TI filename. The -N option changes the host filename, not the TI filename. It is therefore only useful for short TIFILES files, e.g., for use with the Classic 99 emulator.

If we want to view the metadata information of a TIFILES or v9t9 file, we can use the info option -I.

$ xdm99.py -I ashello.asm.tfi
ASHELLO       5  DIS/VAR 80     938 B  63 recs     2020-03-15 17:59:10 C

If we want to see the contents, we use the print -P option instead.

$ ../xdm99.py -P ashello.asm.tfi
*  HELLO WORLD

       IDT 'ASHELLO'

       REF VSBW,VMBW,VWTR
       REF KSCAN
...

To convert from between TIFILES/v9t9 files and plain files, we can use the from and to options -F and -T, where the reference is the TIFILES/v9t9 format. Since plain files lack metadata information, we need to add that data with the file type option -f and the name option -n.

$ xdm99.py -F hello-s.tfi
$ xdm99.py -T ashello.asm -f dv80 -n HELLO-S -o hello-s.tfi

Note that -F, -I, and -P infer automatically whether the file is in TIFILES or v9t9 format. We can still override the format with -t or -9, though.

Analyzing Disks

The check disk option -C analyzes a disk image for errors and prints a summary to stderr. While all disk operations, including cataloging, also check and report any disk errors found, the -C parameter restricts the output of xdm99 to those errors only.

$ xdm99.py -C work.dsk

The -C parameter also causes xdm99 to set its return value to non-zero for warnings, making it simple to write shell scripts for batch processing bad disk images.

The disk repair option -R tries to fix any disk errors, mostly by deleting erroneous files from it.

$ xdm99.py -R bad.dsk
$ xdm99.py -R bad.dsk -o fixed.dsk

The repair operation is likely to cause data loss, so it is best to extract erroneous files beforehand or to specify an alternative output file with -o.

The initialize option -X creates a new, blank disk image, using an optional name provided by -n.

$ xdm99.py blank.dsk -X 720 -n BLANK

The size of the disk image is given by the number of sectors. You may also use a disk geometry string, which is any combination of the number of sides <n>S, the density <n>D, and an optional number of tracks <n>T, where <n> is an integer or the letters S or D. If <n>T is missing, 40T is assumed.

$ xdm99.py blank.dsk -X DSDD
$ xdm99.py blank.dsk -X 1d2s80t

xdm99 cannot create disk images with more than 1600 sectors or with 2S2D80T geometry.

The special geometry CF is used for disk images for the CF7+/nanoPEB devices and corresponds to 1600 sectors.

$ xdm99.py volume.dsk -X cf

You can combine -X with other parameters such -a to work with the newly created image immediately:

$ xdm99.py work.dsk -X SSSD -a file -f DV80

The disk resize option -Z will change the total number of sectors of the disk without changing the contents of the files currently stored.

$ xdm99.py work.dsk -Z 720

An integer argument will not change the geometry information of the disk. To change both size and geometry, -Z also accepts a disk geometry string:

$ xdm99.py corcomp.dsk -Z dssd80t -o ti-80t.dsk  # convert to 80 tracks

Resizing fails if more sectors are used than the target size specifies.

The geometry option --set-geometry explicitly sets the number of sides, the density, and the number of tracks of the disk image.

$ xdm99.py work.dsk --set-geometry 2S1D80T

The --set-geometry command is rarely required for regular images but may be helpful for experimenting with non-standard disk image formats.

The sector dump option -S prints the hexadecimal contents of individual sectors to stdout. This can be used to further analyze disk errors or to save fragments of corrupted files.

$ xdm99.py work.dsk -S 1
00:  00 02 00 03  00 04 00 05  00 06 00 07  00 08 00 09   .... .... .... ....
10:  00 0A 00 0B  00 0C 00 0D  00 0E 00 0F  00 10 00 11   .... .... .... ....
20:  00 12 00 13  00 14 00 15  00 16 00 17  00 18 00 19   .... .... .... ....
30:  00 1A 00 1B  00 1C 00 1D  00 1E 00 1F  00 20 00 21   .... .... .... . .!
40:  00 22 00 23  00 24 00 25  00 26 00 27  00 28 00 29   .".# .$.% .&.' .(.)
50:  00 2A 00 2B  00 2C 00 2D  00 2E 00 2F  00 30 00 31   .*.+ .,.- .../ .0.1
60:  00 32 00 33  00 34 00 35  00 36 00 37  00 38 00 39   .2.3 .4.5 .6.7 .8.9
70:  00 3A 00 3B  00 3C 00 3D  00 3E 00 3F  00 40 00 41   .:.; .<.= .>.? .@.A
80:  00 42 00 43  00 44 00 45  00 46 00 47  00 48 00 49   .B.C .D.E .F.G .H.I
90:  00 4A 00 4B  00 4C 00 4D  00 4E 00 4F  00 50 00 51   .J.K .L.M .N.O .P.Q
A0:  00 52 00 53  00 54 00 55  00 56 00 57  00 58 00 59   .R.S .T.U .V.W .X.Y
B0:  00 5A 00 5B  00 5C 00 5D  00 5E 00 5F  00 60 00 61   .Z.[ .\.] .^._ .`.a
C0:  00 62 00 63  00 64 00 65  00 66 00 67  00 68 00 69   .b.c .d.e .f.g .h.i
D0:  00 6A 00 6B  00 6C 00 6D  00 6E 00 6F  00 70 00 71   .j.k .l.m .n.o .p.q
E0:  00 72 00 73  00 74 00 75  00 76 00 77  00 78 00 79   .r.s .t.u .v.w .x.y
F0:  00 7A 00 7B  00 00 00 00  00 00 00 00  00 00 00 00   .z.{ .... .... ....

Of course, we can redirect output with -o.

$ xdm99.py work.dsk -S 0x22 -o fdr.txt

For convenience, integer arguments of -S, -X and -Z may be specified in decimal or, with > or 0x, hexadecimal notation.

xhm99 HFE Image Manager

The xhm99 HFE image manager is an extension to the xdm99 disk manager that is both a conversion tool and a manager for HFE images used by the HxC floppy emulators.

Converting Images

To convert disk images to HFE images, or vice versa, we use the to HFE and from HFE options, -T and -F. Each option takes an arbitrary number of files.

$ xhm99.py -T work.dsk
$ xhm99.py -T work.dsk -o work_dsk.hfe
$ xhm99.py -F *.hfe

By default, HFE images end in .hfe.

Managing Image Contents

All options other than -F and -T are similar to those of xdm99 and operate directly on the disk image that is contained in the HFE image supplied.

To show the contents of a HFE image, we invoke xhm99 with no options.

$ xhm99.py image.hfe
SOMEDISK  :     4 used  356 free   90 KB  1S/1D 40T  9 S/T
----------------------------------------------------------------------------
SOMEFILE       2  DIS/FIX 60      60 B    1 recs  2016-08-18 20:50:12

To show the contents of a file on the console, use the print argument -P.

$ xhm99.py image.hfe -p SOMEFILE
Hello xdt99, meet HFE!

You may also add, extract, rename, or delete files:

$ xhm99.py image.hfe -a manual.txt -f dv80
$ xhm99.py image.hfe -r MANUAL:README
$ xhm99.py image.hfe -e SOMEFILE -o greeting.txt
$ xhm99.py image.hfe -d SOMEFILE

We can create new HFE images with the initialize option -X. Again, we can combine -X with other options.

$ xhm99.py new.hfe -X dssd -a hello-s.tfi -t

We can also resize HFE images, e.g., if we want to create more free space:

$ xhm99.py sssd.hfe -Z dssd

The resize argument -Z can even change the number of tracks, e.g., converting from DSDD with 40 tracks to DSSD with 80 tracks:

$ xhm99.py dsdd_image.hfe -Z dssd80t

Note that the disk geometry DSDD80T is currently not supported.

For further information about available arguments, please refer to the xdm99 section.

xvm99 nanoPEB Volume Manager

The xvm99 volume manager is an extension to the xdm99 disk manager that is both a conversion tool and a manager for CF card volumes used by nanoPEB/CF7+ devices.

Managing Volumes

All options require a device name and list of volume numbers. xvm99 invoked without any options prints a short summary of the disk images stored in the specified volumes.

$ xvm99.py /dev/sdc 1-4,8
[   1]  EXTBASIC  :     4 used  1596 free
[   2]  EMPTY     :     2 used  1598 free
[   3]  SSSD      :    39 used  1561 free
[   4]  INFOCOM   :   459 used  1141 free
[   8]  (not a valid disk image)

The device name is the name or the port our CF card is connected to. Device names differ by platform, as well as the method to find out what the correct device name is.

Platform Sample device name Command to get device name
Linux /dev/sdc fdisk -l
MacOS /dev/disk3 diskutil list
Windows \.2 wmic diskdrive list brief (DeviceID)

Note that we need to be Administrator or root in order to access the device. On Linux, we can use sudo, and on Windows, we should start the cmd.exe command prompt as administrator.

Note that the device names listed above are examples only. We need to run above commands every time after we insert a CF card, since the device name can change depending on how many devices are connected.

Caution: Make sure you identify your card device correctly, or you will lose data! You might even delete your harddisk!

The second argument of xvm99 may be a single volume number or a list of value ranges, e.g., 1,3-4,6-10. In general, commands are applied to all volumes.

The write option -w writes a disk image to one or more volumes.

$ xvm99.py /dev/sdc 1,3 -w work.dsk

xvm99 automatically extends the disk image to match the 1600 sector format used by the CF7+ device, unless the --keep-size option is given.

The read option -r reads a disk image from a volume.

$ xvm99.py /dev/sdc 2 -r vol2.dsk

When reading from multiple volumes, the resulting disk images will be renamed automatically. xvm99 trims disk images to match the sector count stored in the image, unless the --keep-size option is given.

Manipulating Volumes

Most commands provided by xdm99 are also available for xvm99.

For example, to catalog a volume, you use the same -i command as for xdm99:

$ xvm99.py /dev/sdc 8 -i

Other commands supported by xvm99 are print files -p, extract files -e, add files -a, delete files -d, check disk -C, and repair disk -R.

Again, if more than one volume is specified, then the command is applied to all volumes. For example,

$ xvm99.py /dev/sdc 1-20 -a README -f DV80

adds the local file README to all disk images in volumes 1 through 20.

Feedback and Bug Reports

The xdt99 tools are released under the GNU GPL, in the hope that fellow TI 99 enthusiasts may find them useful.

Please email bug reports and feature requests to the developer at , or use the issue tracker of the project.