A toolbox of 8-bit chip-emulators, helper code and complete embeddable system emulators in dependency-free C headers (a subset of C99 that compiles on gcc, clang and cl.exe).
Tests and example code is in a separate repo: https://github.com/floooh/chips-test
The example emulators, compiled to WebAssembly: https://floooh.github.io/tiny8bit/
For schematics, manuals and research material, see: https://github.com/floooh/emu-info
@sehugg added WASM support for 8bitworkshop.
You'll need to install EMSDK
first. Then type make.
The directory systems contains a number of header-only 8-bit
computer emulators which can be embedded into applications that
provide keyboard input, and render the emulator's generated
video- and audio-output.
Note that accuracy of the system emulators varies quite a lot, and is mainly defined by what games, demos and tests have been used for testing and improving the emulation.
The following system emulators are provided:
The Sinclair ZX Spectrum is supported as the original 48k model and the improved 128 model with a proper sound chip (the AY-3-8912, which was also used in the Amstrad CPC).
The Zilog Z80 CPU.
- tick-callback with CPU-pin bitmask, called with machine-cycle or single-tick granularity
- fast switch-case instruction decoder generated via python script
- up to 7 wait states can be injected per machine cycle by setting WAIT pins in the CPU tick callback
- all undocumented instructions supported
- internal WZ register and undocumented XF and YF flags supported
- support for interrupt-priority handling (daisy chain) with help from the tick callback
- runs the ZEXDOC and ZEXALL tests
- runs the CPU test of the FUSE ZX Spectrum emulator, with the following exceptions:
- the state of the XF/YF undocumented flags is ignored for indirect BIT test instructions, FUSE doesn't agree here with ZEXALL and I think ZEXALL is right (the state of the XF/YF flags depends on the current state of the internal WZ register)
- FUSE assumes that the PC after a HALT instruction has been incremented, while the chips Z80 emulator doesn't incrmenent the PC, this shouldn't make any difference though
- properly handles sequences of DD/FD prefix bytes
- flexible trap callback for hooking in debuggers and "native code" handlers
- NOT IMPLEMENTED/TODO:
- interrupt mode 0
- refresh cycle in second half of opcode fetch machine cycle
- bus request/acknowledge (BUSRQ/BUSAK pins)
The General Instrument AY-3-8910 sound generator chip and its low-cost variants AY-3-8912 and AY-3-8913 (the 3 variants only differ in the number of provided I/O ports, the 8910 has 2 ports, the 8912 has 1, and the 8913 has none.
- programmable via chip-pin bitmask
- separate tick function called from CPU tick callback, returns true when a new audio sample is ready
Helper code for 8-bit home computer memory systems.
- map 16-bit address ranges to host memory with 1-KByte page granularity
- memory pages can be mapped as RAM, ROM or RAM-behind-ROM via separate read/write pointers
- up to 4 'mapping layers' to simplify bank-switching or memory expansion systems
Helper code for keyboard matrix typically found in 8-bit home computers.
- map host system key- or ASCII-codes to keyboard matrix locations
- up to 12x12 matrix size
- up to 4 configurable modifier keys (for shift keys)
- internal pressed-key-buffer for simultaneously pressed host system keys
- configurable 'sticky count' to lengthen short host-system key presses to give the emulated system enough time to scan the keyboard matrix state
A square-wave beeper found in many simple home computers.
- toggle beeper state on/off from CPU tick callback
- tick function returns true when new audio-sample is ready
Helper function to convert a clock frequency in Hz to a number of ticks, and to keep track of the 'left over' ticks from one frame to the next.