Z80 /WAIT signal question

Jon Elson elson at pico-systems.com
Thu Apr 21 23:18:52 CDT 2016

On 04/21/2016 12:36 PM, Eric Smith wrote:
> A friend building a Z80 system asked me about whether the Z80 /WAIT
> signal has any effect during machine cycles that aren't
> memory/IO/intack cycles (i.e., neither /MREQ and /IORQ asserted). The
> user manual only describes the use of /WAIT for adding wait states, so
> I expect it probably only affects mem/IO/intack cycles, but I can't
> find anything definitive in the user manual.
Oh, boy!  I ought to know this one, but really don't.  I 
never tried to use it except on some kind of data cycle.
It could, possibly, depend on what implementation of the 
Z-80 you are using.  I built some battery-powered stuff 
using a Harris Z-80 clone that was all CMOS.  Some timings 
were a bit different from a Zilog Z-80.


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