The Apple I rom monitorI'm not sure if this code is yet copyrighted or not, my primary goal was to revive a piece of history and, maybe, find something that can be yet usefull for little 6502 project. The first Apple have a little 256 bytes assembler rom monitor, a very nice code that can read and write in hex the 6502 memory. The code start at FF00 and end 2 bytes just before the NMI and RESET vectors. I have adapted it preserving the most usefull entry, using some NOP so the routines are at the same original address. Apple I have a typewriter like interface with the msb set to 1, so i've ORA $80 what came in and EOR $80 the output, making it compatible with a normal ascii i/o, cutting away the handshake control. The i/o system routines are trapped from the lib6502, used for running the monitor, at FFF8 and FFF9 respectly. The project can be easilly compiled via ca65 and integrated, if needed, in other project as a debug tool Enjoy! |
