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-$033C memory layout as the C64.
- does not support tape (device 1).
- GEOS is fully compatible with the C64 version.
New Features
- F-keys: F1:
LIST F2: MONITOR F3: RUN F4: <switch 40/80> F5: LOAD F6: SAVE" F7: DOS"$ 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 commandVPEEK(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 banksOV0..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
| 0 |
BASIC |
BASIC interpreter |
| 1-3 |
– |
[Currently unused] |
| 4 |
GEOS |
GEOS KERNAL |
| 5 |
CBDOS |
The computer-based CBM-DOS for FAT32 SD cards |
| 6 |
KEYMAP |
Keyboard layout tables |
| 7 |
KERNAL |
character sets (uploaded into VRAM), MONITOR, KERNAL |
RAM Map
- fixed RAM:
- $0000-$0400 KERNAL/BASIC/DOS system variables
- $0400-$0800 currently unused
- $0800-$9F00 BASIC RAM
- banked RAM:
- banks 0-254: free for applications
- bank 255: DOS buffers and variables
Credits
KERNAL, BASIC and GEOS additions, DOS: Michael Steil, www.pagetable.com; 2-clause BSD license
FAT32 and SD card drivers: Copyright (c) 2018 Thomas Woinke, Marko Lauke, www.steckschein.de; MIT License
Release Notes
Release 31
- correct ROM banking:
- BASIC and KERNAL now live on separate 16 KB banks ($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