Commander X16 BASIC/KERNAL/DOS ROM

This is the Commander X16 ROM containing BASIC, KERNAL and DOS. BASIC and KERNAL are derived from the Commodore 64 versions.

• 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).

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.
• RS232 and IEC are not working.
• PS/2 and SD have issues on real hardware.

ROM Map

• fixed ROM ($E000-$FFFF): KERNAL
• banked ROM ($C000-$DFFF):
  • bank 0: BASIC
  • bank 1: UTIL (monitor)
  • bank 2: DOS

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

KERNAL and BASIC additions, DOS: Michael Steil, www.pagetable.com; 2-clause BSD license

FAT32 and SD card drivers: Copyright (c) 2018 Thomas Woinke, Marko Lauke, www.steckschein.de; MIT License

Release Notes

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