punch

Punch is a virtual computer system that draws inspiration from iconic computing platforms such as the Commodore 64, Amiga 500, and Atari ST. Notable features include:

• Utilization of the MC6809 CPU using the MC6809 library
• A total of 16MB of video RAM, 64KB directly accessible by the CPU
• Screen resolution of 320x200 pixels, refresh rate of 60Hz
• Blitter chip for fast graphics processing
• Programmable using either MC6809 assembly or the Squirrel Programming Language

Table of Contents

• Memory Model
• Blitter

Screenshots

Startup screen

Debug screen

Memory Map

Addressable by MC6809 and Blitter

work in progress

• $000-$0ff direct page (default after reset)
• $100-$3ff available ram and system stack pointer (768 bytes)
• $0400-$0fff input/output area
  • $400-$41f core
    • $800 status register
    • $801 control register
  • $420-$43f timer
  • $440-$45f commander (scripting engine)
  • $500-$5ff keyboard
    • $500 status register
    • $501 control register (writing only)
    • $502/$503 keyboard repeat delay ms (16 bit unsigned)
    • $504/$505 keyboard repeat speed ms (16 bit unsigned)
    • $506 pop keyboard event (reading only)
    • $580-$5ff keyboard state
  • $600-$7ff sound (big endian)
    • $600-$61f sid 0
    • $620-$63f sid 1
    • $640-$65f sid 2
    • $660-$67f sid 3
    • $680-$69f sid 0 (all registers readable)
    • $6a0-$6bf sid 1 (all registers readable)
    • $6c0-$6df sid 2 (all registers readable)
    • $6e0-$6ff sid 3 (all registers readable)
    • $700-$71f analog 0
    • $720-$73f analog 1
    • $740-$75f analog 2
    • $760-$77f analog 3
    • $780-$78f delays (wip)
    • $790-$79f mixer
    • $7a0-$7ff (wip) reserved * $e00-$eff blitter
  • $800-$8ff blitter base page
    • $800 status register (unused)
    • $801 control register
      • write 0b00000001: blit source to destination surface
      • write 0b00000010: tile blit source/dest/tile
      • write 0b00000100: clear destination surface with drawing color
      • write 0b00001000: pset
      • write 0b00010000: line
      • write 0b00100000: rectangle
      • write 0b01000000: solid rectangle
    • $802 source surface pointer (lowest nibble only)
    • $803 destination surface pointer (lowest nibble only)
    • $804 tile surface pointer (lowest nibble)
    • $805 drawing color
    • $808-$809 x0 for drawing operations (16 bit signed)
    • $80a-$80b y0 for drawing operations (16 bit signed)
    • $80c-$80d x1 for drawing operations (16 bit signed)
    • $80e-$80f y1 for drawing operations (16 bit signed)
    • $810-$813 vram peek base address (24 bits, $e10 always #$00)
    • $818 added alpha value during blits
    • $819 added gamma red during blits
    • $81a added gamma green during blits
    • $81b added gamma blue during blits
    • $81c added gamma r, g and b (write only)
  • $900-$9ff blitter vram poke / peek page (see $810-$813)
  • $a00-$aff blitter surface descriptors (16 in total, 16 bytes each)
    • $ax0-$ax1 x position (16 bit signed)
    • $ax2-$ax3 y position (16 bit signed)
    • $ax4-$ax5 w width (16 bit unsigned)
    • $ax6-$ax7 h height (16 bit unsigned)
    • $ax8-$axb base address of surface data ($ax8 will always contain $00)
    • $axc flags_0
    • $axd flags_1
    • $axe flags_2
    • $axf index ("sprite pointer")
  • $b00-$bff reserved
  • $c00-$fff color table (32 bits color, 256 values, for 1, 2, 4 and 8 bit modes)
  • $1000-$1fff color index tables (for 1, 2, 4 and ...)
• $2000-$fbff 55kb ram ($fc00 is initial usp)
• $fc00-$ffff 1kb kernel + vectors

Addressable by Blitter only

• $010000-$ffffff available vram (16.320kb) of which:
• $f00000-$f2d8ff default framebuffer vram (182kb)
• $f3e800 draw color, 32 bit, stored in vram (is this correct)

Building with CMake

Create a build directory in the source tree mkdir build, run cmake .. from that directory and run make. Alternatively do mkdir Debug, run cmake -DCMAKE_BUILD_TYPE=Debug .. from that directory and run make.

Below some more OS specific intructions on how to prepare the build environment.

MacOS specific

• Install Xcode from App Store
• When it asks to install command line tools, do that
• Install Homebrew
• From the Homebrew command line, install cmake and SDL2 libraries

Ubuntu / Debian specific

To be done

Windows specific

To be done

Websites and projects of interest

• CCS64 - A Commodore 64 Emulator by Per Håkan Sundell.
• Commander X16 - The Commander X16 is a modern 8-bit computer currently in active development. It is the brainchild of David "the 8 Bit Guy" Murray.
• Commander X16 emulator - Software version of Commander X16.
• freeverb - Free, studio-quality reverb SOURCE CODE in the public domain
• Hatari - Hatari is an Atari ST/STE/TT/Falcon emulator.
• lib65ce02 - CSG65CE02 emulator written in C.
• MC6809 - MC6809 cpu emulator written in C++.
• Mega65 - The 21st century realization of the C65 heritage.
• Moira - Motorola 68000 cpu emulator written in C++ by Dirk W. Hoffmann.
• reSID - ReSID is a Commodore 6581 and 8580 Sound Interface Device emulator by Dag Lem.
• SDL Simple DirectMedia Layer - A cross-platform development library by Sam Lantinga designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware.
• Squirrel - Squirrel is a high level imperative, object-oriented programming language, designed to be a light-weight scripting language that fits in the size, memory bandwidth, and real-time requirements of applications like video games.
• stb - single-file public domain (or MIT licensed) libraries for C/C++
• TIC-80 - TIC-80 is a free and open source fantasy computer for making, playing and sharing tiny games.
• vAmiga - An Amiga 500, 1000, or 2000 on your Apple Macintosh by Dirk W. Hoffmann.
• vasm - A portable and retargetable assembler.
• VICE - The Versatile Commodore Emulator.
• VirtualC64 - A Commodore 64 on your Apple Macintosh by Dirk W. Hoffmann.
• visual6502 - Visual Transistor-level Simulation of the 6502 CPU and other chips.

MIT License

Copyright (c) 2023-2025 elmerucr

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.