|
Post by dshadoff on Feb 6, 2021 18:00:14 GMT
I'm researching making an additional piece of hardware for the PC Engine, and wanted to confirm the memory map in the $FF bank.
Since there is so much aliasing of memory locations (due to address-decode using less-than-100% of the address lines in the decode algorithm), large blocks of memory are aliased for existing peripherals, rendering those areas "in use". I wanted to confirm which memory areas are still available for mapping:
Areas in Bank $FF which are already in use: $0000-$03FF = VDC (Hu6270) (*1) $0400-$07FF = VCE (Hu6260) (*1) $0800-$0BFF = PSG (*2) $0C00-$0FFF = Timer (*2) $1000-$13FF = I/O (especially joypad) ** (*3) $1400-$1700 = Interrupt request/Interrupt Disable (*3) $1800-$19FF = CD-ROM (*2) $1A00-$1AFF = Arcade Card $1B00-$1BFF = SSDS3 improperly aliases Arcade Card to here; will cause incompatibility if used $1C00-$1FFF = empty ??
*1 = These are known to be aliased across the entire range *2 = These are suspected to be aliased, but I don't have confirmation *3 = How many other things are in these ranges ? Are they aliased at all ?
Please let me know any details for the missing information, or if I've overlooked anything. I will update this post with any additional information.
|
|
|
Post by ccovell on Feb 7, 2021 13:08:01 GMT
Hmm... well, the Hu7 development interface uses $1C00-1C40. Not that that affects more than 0.001% of PCEs out there.
|
|