README.md

Commander X16 Emulator

This is an emulator for the Commander X16 computer system. It only depends on SDL2 and should compile on all modern operating systems.

Starting

You can start x16emu/x16emu.exe either by double-clicking it, or from the command line. The latter allows you to specify additional arguments.

• When starting x16emu without arguments, it will pick up the system ROM (rom.bin) and the character ROM (chargen.bin) from the executable's directory.
• The system ROM and character ROM filenames/paths can be overridden with the -rom and -char command line arguments.
• -sdcard lets you specify an SD card image (partition table + FAT32).
• -prg leys you specify a .prg file that gets injected into RAM after start.
• When compiled with #define TRACE, -trace will enable an instruction trace on stdout.

Run x16emu -h to see all command line options.

Functions while running

• Cmd + R will reset the computer.
• Cmd + S will save a memory dump (40 KB main RAM + 2 MB bankable RAM) to disk.

(These shortcuts currently only work on macOS.)

Host Filesystem Interface

If the system ROM contains any version of the KERNAL, the LOAD ($FFD5) and SAVE ($FFD8) KERNAL calls are intercepted by the emulator if the device is 1 (which is the default). So the BASIC statements

  LOAD"$
  LOAD"FOO.PRG
  LOAD"IMAGE.PRG",1,1
  SAVE"BAR.PRG

will target the host computer's local filesystem.

Using the KERNAL/BASIC environment

Please see the KERNAL/BASIC documentation.

Features

• CPU: Full 65C02 instruction set (improved "fake6502")
• VERA
  • Mostly cycle exact emulation
  • Supports almost all features: composer, two layers, sprites, progressive/interlaced
• VIA
  • ROM/RAM banking
  • PS/2 keyboard
  • SD card (SPI)
• A 60 Hz interrupt is injected independently of the VIA settings.

Missing Features

• VERA
  • Does not support IRQs
  • Does not support the "CURRENT_FIELD" bit
  • Does not sprite z-depth, collisions or limitations
  • Only supports the first 16 sprites
  • Interlaced modes (NTSC/RGB) don't render at the full horizontal fidelity
• VIA
  • Does not support counters/timers/IRQs
  • Does not support game controllers
• Sound
  • No support

License

Copyright (c) 2019 Michael Steil <[email protected]>, www.pagetable.com. All rights reserved. License: 2-clause BSD

Release Notes

Release 28

• support for 65C02 opcodes [Paul Robson]
• keep aspect ratio when resizing window [Sebastian Voges]
• updated sprite logic to VERA 0.7 – the layout of the sprite data registers has changed, you need to change your code!

Release 27

• Command line overhaul. Supports -rom, -char, -sdcard and -prg.
• ROM and char filename defaults, so x16emu can be started without arguments.
• Host Filesystem Interface supports LOAD"$"
• macOS and Windows packaging logic in Makefile

Release 26

• better sprite support (clipping, palette offset, flipping)
• better border support
• KERNAL can set up interlaced NTSC mode with scaling and borders (compile time option)

Release 25

• sdcard: fixed LOAD,x,1 to load to the correct addressg
• sdcard: all temp data will be on bank #255; current bank will remain unchanged
• DOS: support for DOS commands ("UI", "I", "V", ...) and more status messages (e.g. 26,WRITE PROTECT ON,00,00)
• BASIC: "DOS" command. Without argument: print disk status; with "$" argument: show directory; with "8" or "9" argument: switch default drive; otherwise: send DOS command; also accessible through F7/F8
• Vera: cycle exact rendering, NTSC, interlacing, border

Release 24

• SD card support
  • pass path to SD card image as third argument
  • access SD card as drive 8
  • the local PC/Mac disk is still drive 1
  • modulo debugging, this would work on a real X16 with the SD card (plus level shifters) hooked up to VIA#2PB as described in sdcard.c in the emulator surce

Release 23

• Updated emulator and ROM to spec 0.6 – the ROM image should work on a real X16 with VERA 0.6 now.

Release 22

SYS65375 (SWAPPER) now also clears the screen, avoid ing side effects.

Release 21

• support for $ and % number prefixes in BASIC
• support for C128 KERNAL APIs LKUPLA, LKUPSA and CLOSE_ALL

Release 20

• Toggle fullscreen using Cmd+F or Cmd+return
• new BASIC instructions and functions:
  • MON: enter monitor; no more SYS65280 required
  • VPEEK(bank, address)
  • VPOKE bank, address, value example: VPOKE4,0,VPEEK(4,0) OR 32 [for 256 color BASIC]

Release 19

• fixed cursor trail bug
• fixed f7 key in PS/2 driver
• f keys are assigned with shortcuts now: F1: LIST F2: <enter monitor> F3: RUN F4: <switch 40/80> F5: LOAD F6: SAVE" F7: DOS"$ <doesn't work yet> F8: DOS <doesn't work yet>

Release 18

• Fixed scrolling in 40x30 mode when there are double lines on the screen.

Release 17

• video RAM support in the monitor (SYS65280)
• 40x30 screen support (SYS65375 to toggle)

Release 16

• Integrated monitor, start with SYS65280 rom.bin is now 3*8 KB:
  • 0: BASIC (bank 0 at $C000)
  • 1: KERNAL ($E000)
  • 2: UTIL (bank 1 at $C000)

Release 15

• correct text mode video RAM layout both in emulator and KERNAL

Release 14

• KERNAL: fast scrolling
• KERNAL: upper/lower switching using CHR$($0E)/CHR$($8E)
• KERNAL: banking init
• KERNAL: new PS/2 driver
• Emulator: VERA updates (more modes, second data port)
• Emulator: RAM and ROM banks start out as all 1 bits

Release 13

• Supports mode 7 (8bpp bitmap).

Release 12

• Supports 8bpp tile mode (mode 4)

Release 11

• The emulator and the KERNAL now speak the bit-level PS/2 protocol over VIA#2 PA0/PA1. The system behaves the same, but keyboard input in the ROM should work on a real device.

Release 10

updated KERNAL with proper power-on message

Release 9

• LOAD and SAVE commands are intercepted by the emulator, can be used to access local file system, like this:

  LOAD"TETRIS.PRG
  SAVE"TETRIS.PRG
  

• No device number is necessary. Loading absolute works like this:

  LOAD"FILE.PRG",1,1
  

Release 8

• New optional override load address for PRG files:

  ./x64emu rom.bin chargen.bin basic.prg,0401
  

Release 7

• Now with banking. POKE40801,n to switch the RAM bank at $A000. POKE40800,n to switch the ROM bank at $C000. The ROM file at the command line can be up to 72 KB now (layout: 0: bank 0, 1: KERNAL, 2: bank 1, 3: bank 2 etc.), and the RAM that Cmd+S saves is 2088KB ($0000-$9F00: regular RAM, $9F00-$9FFF: unused, $A000+: extra banks)

Release 6

• Vera emulation now matches the complete spec dated 2019-07-06: correct video address space layout, palette format, redefinable character set

Release 5

• BASIC now starts at $0401 (39679 BASIC BYTES FREE)

Release 4

• Cmd+S now saves all of memory (linear 64 KB for now, including ROM) to "memory.bin", "memory-1.bin", "memory-2.bin", etc. You can extract parts of it with Unix "dd", like: dd if=memory.bin of=basic.bin bs=1 skip=2049 count=38655

Release 3

• Supports PRG file as third argument, which is injected after "READY.", so BASIC programs work as well.

Release 2

• STOP key support

Release 1

• 6502 core, fake PS/2 keyboard emulation (PS/2 data bytes appear at VIA#1 PB) and text mode Vera emulation
• KERNAL/BASIC modified for memory layout, missing VIC, Vera text mode and PS/2 keyboard