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A place to keep my 6502 breadboard computer assembler programs
Based on the work of Ben Eater https://eater.net/6502
Assembly language .s files are assembled using vasm in 6502 'oldstyle' mode, eg
./vasm6502_oldstyle -Fbin -dotdir monitor2.s
Flashed to EEPROM using minipro:
minipro -p AT28C256 -w a.out
hello world
Prints text to LCD display using RAM for stack pointer and VIA to interface with LCD
Prints some different text with a button connected to VIA CA1 pin
monitor1
Really dreadful code, first steps towards a monitor program. Shows contents of ROM on LCD display: address, hex contents, ASCII representation. Press button on CA1 to advance. Only steps through 256 bytes. Byte to ASCII hex code needs putting in a subroutine. Weird sh&t going on with the X register - had to paste display code in before infinite loop otherwise x was not reset to 0, why this makes any difference beats me. The ASCII offset for converting hex numbers A-F is mad - should be #41 not #30. Why? WHY DOES #41 WORK? IT MAKES NO SENSE.
monitor2
Slightly less dreadful. Folds hex>ascii conversion into subroutines. .out file is raw binary for flashing to EEPROM.
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