store2@ihuxi.UUCP (04/09/87)
HELP!!! I have a 600XL that I modified with a 256K memory upgrade that was compatible with the memory upgrade published in BYTE. I have now decided to modify the circuit to make the memory upgrade compatible with the 130XE. I have modified my circuit based on information published in Antic (Feb. 1987) on how the bank switching of memory works in the 130XE. My modification appears to work fine with the software published in this issue of Antic, but does not work with the ramdisk driver in Sparta Dos. The following are the definitions of the bits in PORTB and signals used by my circuit. PORTB Bits PB2 & PB3 - determine which 16K bank of 4 is used in extended memory mode PB4 - extend memory mode bit for CPU (when low CPU is in extended memory mode) PB5 - extend memory mode bit for ANTIC (when low ANTIC is in extended memory mode) PB6 - unused PB0 & PB1 & PB7 - used to bank switch between ram and basic/os/fp rom Signals used HALT - when low ANTIC accesses memory, when high CPU accesses memory MUX - this is the select lead between the ras address (when low) and the cas address (when high) A15 & A14 & - address bits used (a0 & a7 are for the ras address, A0 & A7 a15 & a14 are for cas address and decoding bank switched area in memory) My questions are: Does anybody see a missing registered bit or signal that needs to be added to this list? Is there a better source of information on the details of using the memory bank switching capabilities of the 130XE? What other registered bits do the other 256K 130XE compatible upgrades use to get to the additional 128K of memory? Wayne Wilcox AT&T-ISL 1100 E. Warrenville Rd. Naperville, IL 60566 ...!ihnp4!ihuxi!store2