Imported from GitHub: rprouse/65C02_SBC · commit 7280d9f · license MIT

Description

Assembly code for my 8-bit 65C02 based breadboard computer

README

8-Bit 65C02 based Computer

This repository contains assembly code for the 65C02 based 8-bit computer I am building on a breadboard. I started out writing the assembly and compiling it using vasm because it is portable to many different CPUs including the Z80 which I also program for. I recently switched to using cc65 because it allows me to specify the memory layout of this machine and ships with the memory layouts of many more machines like the VIC20, C64, Commander X16, Atari consoles, etc.

The breadboard version of this computer is based on the design by Ben Eater. If you are interested in following along, I highly recommend his video series.

After completing the breadboard version, I found an updated version with two VIA chips, a 6551 based ACIA chip for serial communications and a PS/2 keyboard port with an ATtiny4313 based keyboard controller by Dawid Buchwald who writes about the designing the computer on Hackaday.io.

I had boards made by PCBWay.com and built a version of the computer based on David's design. Much of the software here started out being written by David.

Memory Map

Segment	BE6502	DB6502	Comment
RAM	0x0000-0x3FFF	0x0000-0x7FFF
VIA1		0x9000	Connected to keyboard/LCD/blink LED in my build
VIA2	0x6000	0x8800	Can be used to run Ben's programs
ACIA		0x8400
ROM	0x8000-0xFFFF	0xA000-0xFFFF	First 8K are not accessible, but need to be burned to the chip

16x2 LCD addressing scheme

0x00	0x01	0x02	0x03	...	0x0F
0x40	0x41	0x42	0x43	...	0x4F

20x4 LCD addressing scheme

0x00	0x01	0x02	0x03	...	0x13
0x40	0x41	0x42	0x43	...	0x53
0x14	0x15	0x16	0x17	...	0x28
0x53	0x54	0x55	0x56	...	0x68