commodore_64_emulator

a work-in-progress emulator that aims to run BASIC programs, not cycle-accurate.

implemented components:

• 6510 CPU a bit modified version of 6502 (instruction accurate independant emulator)
• VIC-II (Video Interface Chip)

    • 16 KB address space for screen, character, and sprite memory
    • 320 × 200 pixels video resolution (160 × 200 in multicolor mode)
    • 40 × 25 characters text resolution
    • 8 hardware sprites, each 24 × 21 pixels (12 × 21 in multicolor mode)
    • 16 colors
    • Raster interrupts for advanced effects and timing control
    • Smooth scrolling
    • Three character display modes and two bitmap modes:
      - Standard Character Mode
      - Multicolor Character Mode
      - Extended Background Color Mode
      - Standard Bitmap Mode
      - Multicolor Bitmap Mode
  

• CIA-1 & CIA-2 (Complex Interface Adapters)

    • keyboard input scanning for detecting key presses
    • timer A & Timer B in each chip for generating delays and timing events
    • memory management registers for I/O mapping and bank switching
    • time of Day (TOD) clock
  

basic functionality test

some one line BASIC programs at ./programs/bas/10_print.bas

10 PRINT CHR$(205.5+RND(1)); : GOTO 10

10 PRINT CHR$(32+(INT(RND(1)+.5)*81)); : GOTO 10

shell interface

it has a small shell that runs in a separate thread for debugging
and general hardware behaviour observation:

command	description
LDP [path]	Load a BASIC program (.prg) into memory.
LDD [path]	Load a (.d64) D64 disk image.
-	-
DMP $st $en	Dump memory from address $st to $en.
SCR	Show CPU status/registers.
SVR	Show VIC-II status/registers.
SC1	Show CIA#1 status/registers.
SC2	Show CIA#2 status/registers.
-	-
BRD [1-16]	Change the border color.
BGR [1-16]	Change the background color.
TXT [1-16]	Change the text color.
-	-
CLR	Clear the loaded program from memory and perform a hard reset.
EXT	Exit the emulator.

graphic libraries:

uses SDL3 as the main library.
however the v1.0 branch still uses MLX42, a lightweight library on top of GLFW.

requirements

• Linux or MacOS
• readline (libreadline-dev)
• cmake >= 3.18
• if trying to compile the v1.0 branch mlx42 needs glfw (libglfw3-dev)

installation

• install dependencies linux

apt update -y && apt install -y libdreadline-dev cmake

or macos

brew install cmake readline

• clone this repository and cd to it

git clone https://github.com/beddinao/commodore_64_emulator.git && cd commodore_64_emulator 

• compile and run

make && ./c64_emu

screenshots

animated demos

basic games

some art brought from the C64 demoScene

upcoming features:

• Full hardware sprite support (partial-progress)
• SID sound emulation (partial-progress)

useful-resources

• C64 Wiki: https://www.c64-wiki.com/wiki/Main_Page
• memory map: https://sta.c64.org/cbm64mem.html
• VIC-II ultimate resource: https://www.zimmers.net/cbmpics/cbm/c64/vic-ii.txt
• 6502 ultimate resource: https://www.masswerk.at/6502/6502_instruction_set.html
• 6502 BCD: http://www.6502.org/tutorials/decimal_mode.html