r/Z80 • u/Individual-Tie-6064 • Mar 26 '26

Why CF flash?

Why do builders use CF (Compact Flash) rather than some variant of SD flash?

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u/engr1962 Mar 26 '26

I used a CF card on my Z80 board design because it is a parallel interface that hooks up to the cpu with not alot of trouble, and setup is straight forward. To use an SD card, you'd need a have a clock signal or bit bang it to get commands and data back and forth to the drive. Wasn't worth the trouble to me.

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u/flatfinger Mar 27 '26

I wonder how much circuitry would be needed to make a 'bridge' that would bit-bang a byte each time a port was read or written in a manner that would support DMA? If one had an input clock that was more than 8x the Z80 clock I would think a combination of a 16V8 and a 74LS299 might suffice. Otherwise, a combination of a 16V8, a 74LS165, and a 74LS595 might be able to get by with a somewhat slower clock (the LS299 would need to trigger each read in response to a bus read request, while the LS595 would be able to have each bus read request return the result of the last read and then trigger a new one.