Michael wrote:
One last idea, if I may? If you're simply trying to reduce the chip count and you don't mind dedicating an 8K block for I/O, how about a single 74xx139 decoder/glue IC and borrow Daryl Rictor's trick from the "6502 Badge" and use the ROM write strobe to write to the '273? Drawing below (yes, it still requires a 64K or 128K SRAM IC)...
Regards...
That is exactly what I was going for in the OP! I wonder if there’s an easy way around the second CS for the RAM.
When I’m ready for the next real revision this will get some serious consideration - if this and a single other gate is all I need(to make up for using a 62256), it looks like I can reduce chip count without increasing total cost.
(Going for cheap, easy to source second hand, nostalgic, and small footprint - in about that order)
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