MEMORY ORGANISATION The 80-column expansion ROM can be accessed after reading from or writing to any location within $C300 - $C3FF. It is turned off by accessing $CFFF. For all I/O firmwares, their expansion ROM can be turned off by accessing SCFFF. If reading from or writing to that I/O firmware entry point region, their expansion ROM will be automatically turned on. • The parallel printer and serial printer share the same expansion ROM ($C800 - $CFFF) so only one type of printer can be active at any one time. • RS232 firmware occupies the memory address range $C200 - $C2FF. • The mouse firmware only occupies $C400 - $C4FF.
Accessing any location in this range cannot affect any $C800-$CFFF expansion ROM. • The 1M RAM expansion firmware occupies locations from $C500 - $C5FF. • The 5.25" floppy disk drive controller firmware occupies locations from $C600- $C6FF. • The 3.5" disk drive firmware occupies locations from $C700 - SC7FF. 3-6