Hand clocking CPUs
eric at brouhaha.com
Wed Jul 21 16:22:33 CDT 2010
JP Hindin wrote:
> Has anyone -tried- hand-clocking a Z80?
Won't work on an original NMOS Z80 CPU, they were definitely dynamic.
You could get away with somewhat slower than the minimum spec (about
246.3 kHz for a 4MHz NMOS Z80), but not at finger speed.
Some of the later CMOS Z80 cores are static, some are not. In
particular, the original Z180 was CMOS but dynamic. It may be the case
that all CMOS Z80 CPUs (vs. Z180 and other derivatives) are static, I'm
not sure. Check the data sheet for the specific part number you're using.
If you hand-clock a static CPU, remember to debounce your button or
switch. Switch bounce can have glitches faster than the minimum clock
pulse width spec; I've seen them on an oscilliscope many times. Even
if you don't get fast glitches, you'll still get multiple pulses when
only one is desired.
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