3 ms·
http://forum.6502.org/viewtopic.php?f=1&t=2027 http://forum.6502.org/viewtopic.php?f=1&t=2027 "The datasheet describes it as a 6502 instruction set, with an X
by pinewurst 8y ago
http://forum.6502.org/viewtopic.php?f=1&t=2027 http://forum.6502.org/viewtopic.php?f=1&t=2027
"The datasheet describes it as a 6502 instruction set, with an X register but no Y, and just 69 "instructions" (presumably opcodes, of which the 6502 has 151). It has a banked ROM architecture and just 128 bytes of RAM at $80 through $FF which "includes stack" - so page one is folded onto page zero presumably."
- monocasa 8y agoOK, it does look like a Sunplus SPC81A, like they said. Memory map, interrupts, I/O registers all match. http://www.ic72.com/pdf_file/-/428557.pdf http://www.ic72.com/pdf_file/-/428557.pdf FWIW though, it doesn't loo like page one is an alias of page zero, but is instead unmapped. That's not the biggest deal in the world to the zero page the fixed stack page given that this is probably a totally different mask set than a regular 6502. I wonder if you can underrun the stack into the HW registers or if their stack pointer is only 7 bits?