Microprocessor Control Of Ram And Rom - Commodore 1540 Service Manual

1541 CIRCUIT THEORY

Microprocessor Control of RAM and ROM

UB3 and UB4 are 8192 x 8 bit ROMS that store the Disk Operating System (DOS). UB3 resides at memory
locations $C000-$DFFF. UB4 resides at memory locations $E000-$FFFF. UC5 and UC6 decodes the addresses
output from the microprocessor when selecting these ROMS.
UB2 is a 2048 x 8 bit RAM. UB2 resides at memory locations $0000-$07FF. This memory is
used for processor stack operations, general processor housekeeping, use program storage,
and 4 temporary buffer areas. UC5, UC6 and UC7 decode the addresses output from the
processor when selecting RAM.