Commander X16 BASIC/KERNAL/DOS/GEOS ROM

This is the Commander X16 ROM containing BASIC, KERNAL, DOS and GEOS. BASIC and KERNAL are derived from the Commodore 64 versions. GEOS is derived from the C64/C128 version.

• BASIC is fully compatible with Commodore BASIC V2.
• KERNAL
  • supports the complete $FF81+ API.
  • has the same zero page and $0200-$033C memory layout as the C64.
  • does not support tape (device 1).
• GEOS is fully compatible with the C64 version.

Releases and Building

Each release of the X16 emulator includes a compatible build of rom.bin. If you wish to build this yourself (perhaps because you're also building the emulator) see below.

WARNING: The emulator will currently work only with a contemporary version of rom.bin; earlier or later versions are likely to fail.

Building the ROM

Building this source code requires only GNU Make and the cc65 assembler. GNU Make is almost invariably available as a system package with any Linux distribution; cc65 less often so.

• Red Hat: sudo yum install make cc65
• Debian: sudo apt-get install make

On macOS, cc65 in homebrew, which must be installed before issuing the following command:

• macOS: brew install cc65

If cc65 is not available as a package on your system, you'll need to install or build/install it per the instructions below.

Once the prerequisites are available, type make to build rom.bin. To use that with the emulator, copy it to the same directory as the x16emu binary or use x16emu -rom .../path/to/rom.bin.

Building/Installing cc65

Linux Builds from Source

You'll need the basic set of tools for building C programs:

• Debian/Ubuntu: sudo apt-get install build-essential git

The cc65 source is on GitHub; clone and build it with:

git clone https://github.com/cc65/cc65.git
make -j4    # -j4 may be left off; it merely speeds the build

This will leave the binaries in the bin/ subdirectory; you may use thes directly by adding them to your path, or install them to a standard directory:

#   This assumes you have ~/.local/bin in your path.
make install PREFIX=~/.local

Building and Packages for Other Systems

Consult the Nesdev Wiki Installing CC65 page for some hints, including Windows installs. However, the Debian packages they suggest from trikaliotis.net appear to have signature errors.

New Features

• F-keys: F1: LIST F2: MONITOR F3: RUN F4: <switch 40/80> F5: LOAD F6: SAVE" F7: DOS"$ F8: DOS
• New BASIC instructions
  • MONITOR: see below.
  • DOS: no argument: read disk status. "8" or "9" as an argument: switch default drive. "$" as an argument: show directory. all other arguments: send DOS command
  • VPEEK(bank, offset), VPOKE bank, offset, value to access video memory. "offset" is 16 bits, "bank" is bits 16-19 of the linear address. Note that the tokens for the new BASIC commands have not been finalized yet, so loading a BASIC program that uses the new keywords in a future version of the ROM will break!
• Support for $ and % in BASIC expressions for hex and binary
• LOAD prints the start and end(+1) addresses
• Integrated Monitor derived from the Final Cartridge III.
  • O00..OFF to switch ROM and RAM banks
  • OV0..OV4 to switch to video address space
• FAT32-formatted SD card as drive 8 as a full IEC (TALK/LISTEN & CBM DOS) compatible device:
  • read directory
  • load file
  • send "I" command
  • read status
  • everything else is unimplemented
• Some new KERNAL APIs (to be documented)

Big TODOs

• DOS needs more features.
• BASIC needs more features.
• IEC is not working.
• PS/2 and SD have issues on real hardware.

ROM Map

RAM Map

• fixed RAM:
  • $0000-$0400 KERNAL/BASIC/DOS system variables
  • $0400-$0800 currently unused
  • $0800-$9F00 BASIC RAM
• banked RAM:
  • banks 0-254: free for applications
  • bank 255: DOS buffers and variables

Credits

• All new code, and additions to legacy code: ©2020 Michael Steil, www.pagetable.com; 2-clause BSD license
• FAT32 and SD card drivers: ©2018 Thomas Woinke, Marko Lauke, www.steckschein.de; MIT License
• kernal/open-roms: ©2019 Paul Gardner-Stephen, 2019; GPLv3 license
• kernal/cbm: ©1983 Commodore Business Machines (CBM)
• basic: ©1977 Microsoft Corp.
• geos: ©1985 Berlekey Softworks

Release Notes

Release 36 ("Berlin")

• API Features

  • added console API for text-based interfaces with proportional font and styles support: console_init, console_put_char, console_get_char
  • added memory API:
    • memory_fill
    • memory_copy
    • memory_crc
    • memory_decompress (LZSA2)
  • added sprite API: sprite_set_image, sprite_set_position
  • renamed GRAPH_LL to FB (framebuffer)
  • GRAPH_init takes an FB graphics driver as an argument

• KERNAL features

  • detect SD card on TALK and LISTEN, properly fall back to serial
  • joystick scanning is done automatically in VBLANK IRQ; no need to call it manually any more
  • added VERA UART driver (device 2)
  • bank 1 is now the default after startup; KERNAL won't touch it
  • sprites and layer 0 are cleared on RESET
  • changed F5 to LOAD":* (filename required for IEEE devices)
  • GRAPH_move_rect supports overlapping [gaekwad]

• BASIC

  • default LOAD/SAVE device is now 8
  • added RESET statement [Ingo Hinterding]
  • added CLS statement [Ingo Hinterding]

• CHARSET

  • fixed capital Ö [Ingo Hinterding]
  • Changed Û, î, ã to be more consistent [Ingo Hinterding]

• bug fixes

  • COLOR statement with two arguments
  • PEEK for ROM addresses
  • keyboard code no longer changes RAM bank
  • fixed clock update
  • fixed side effects of Ctrl+A and color control codes [codewar65]

• misc

  • added 3 more tests, start with "TEST1"/"TEST2"/"TEST3" in BASIC:
  • TEST0: existing misc graphics test
  • TEST1: console text rendering, character wrapping
  • TEST2: console text rendering, word wrapping
  • TEST3: console text input, echo

Release 35

• API Fetures

  • new KERNAL API: low-level and high-level 320x200@256c bitmap graphics
  • new KERNAL API: get mouse state
  • new KERNAL API: get joystick state
  • new KERNAL API: get/set date and time (old RDTIM call is now a 24 bit timer)
  • new floating point API, jump table at $FC00 on ROM bank 4 (BASIC)

• KERNAL Features

  • invert fg/bg color control code (Ctrl+A) [Daniel Mecklenburg Jr]

• BASIC

  • added COLOR <fg, bg> statement to set text color
  • added JOY(n) function (arg 1 for joy1, arg 2 for joy2)
  • added TEST statement to start graphics API unit test
  • CHAR statement supports PETSCII control codes (instead of GEOS control codes), including color codes

• misc

  • KERNAL variables for keyboard/mouse/clock drivers were moved from $0200-$02FF to RAM bank #0
  • $8F (set PETSCII-UC even if ISO) printed first after reset [Mikael O. Bonnier]

• bug fixes:

  • got rid of $2c partial instruction skip [Joshua Scholar]
  • fixed TI/TI$
  • fixed CBDOS infinite loop
  • zp address 0 is no longer overwritten by mouse code
  • mouse scanning is disabled if mouse is off
  • VERA state is correctly saved/restored by IRQ code

Release 34

• new layout for zero page and KERNAL/BASIC variables:
  • $00-$7F available to the user
  • ($02-$52 are used if using BASIC graphics commands)
  • $80-$A3 used by KERNAL and DOS
  • $A4-$A8 reserved for KERNAL/DOS/BASIC
  • $A9-$FF used by BASIC
• new BASIC statements:
  • SCREEN <mode> (0: 40x30, 2: 80x60, 128: graphics)
  • PSET <x>, <y>, <color>
  • LINE <x1>, <y1>, <x2>, <y2>, <color>
  • FRAME <x1>, <y1>, <x2>, <y2>, <color>
  • RECT <x1>, <y1>, <x2>, <y2>, <color>
  • CHAR <x>, <y>, <color>, <string>
  • MOUSE <n> (0: off, 1: on)
• new BASIC functions:
  • MX (mouse X coordinate)
  • MY (mouse Y coordinate)
  • MB (mouse button; 1: left, 2: right, 4: third)
• new KERNAL calls:
  • MOUSE: configure mouse
  • SCRMOD: set screen mode
• new PS/2 mouse driver
• charsets are uploaded to VERA on demand
• GEOS font rendering uses less slant for faux italics characters
• misc GEOS KERNAL improvements and optimizations

Release 33

• BASIC
  • additional LOAD syntax to load to a specific address LOAD [filename[,device[,bank,address]]]
  • LOAD into banked RAM will auto-wrap into successive banks
  • LOAD allows trailing garbage; great to just type LOAD into a directory line [John-Paul Gignac]
  • new BASIC statement: VLOAD to load into video RAM: VLOAD [filename[,device[,bank,address]]] [John-Paul Gignac]
  • complete jump table bridge
• KERNAL: memory size detection
• KERNAL: faster IRQ entry
• GEOS: converted graphics library to VERA 320x200@256c

Release 32

• correct ROM banking:
  • BASIC and KERNAL now live on separate 16 KB banks ($C000-$FFFF)
  • BASIC PEEK will always access KERNAL ROM
  • BASIC SYS will have BASIC ROM enabled
• added GEOS
• added OLD statement to recover deleted BASIC program after NEW or RESET
• removed software RS-232, will be replaced by VERA UART later
• Full ISO mode support in Monitor

Release 31

• switched to VERA 0.8 register layout; character ROM is uploaded on startup
• ISO mode: ISO-8859-15 character set, standard ASCII keyboard
• keyboard
  • completed US and UK keymaps so all C64 characters are reachable
  • support for AltGr
  • support for F9-F12
• allow hex and binary numbers in DATA statements [Frank Buss]
• switched SD card from VIA SPI to VERA SPI (works on real hardware!)
• fix: VPEEK overwriting POKER ($14/$15)
• fix: STOP sometimes not registering in BASIC programs

Release 30

• support for 13 keyboard layouts; cycle through them using F9
• GETJOY call will fall back to keyboard (cursor/Ctrl/Alt/Space/Return), see Programmer's Reference Guide on how to use it
• startup message now shows ROM revision
• $FF80 contains the prerelease revision (negated)
• the 60 Hz IRQ is now generated by VERA VSYNC
• fix: VPEEK tokenization
• fix: CBDOS was not correctly preserving the RAM bank
• fix: KERNAL no longer uses zero page $FC-$FE