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 $COOO-$DFFF. UB4 resides at memory locations $EOOO-$FFFF. UC5 and UC6 decode
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, user program storage, and 4 tem
porary buffer areas. UC5, UC6, and UC7 decode the addresses output from the processor when selec
ting RAM.
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