Computing > Vintage Computing

Problems with Z80 DART serial

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SiliconWizard:
Can you try downclocking the CPU just to see if it's the cause?

profdc9:
In order to get a usable baud rate I need to downclock to half the crystal speed, which is why I ordered a 3.6864 MHz crystal, but I could try to inject it using a function generator I suppose.

profdc9:
Well, it's been running off my function generator at 3.6864 MHz for about half an hour now, so it seems to be stable at this frequency.

Maybe it is the slight overclocking...

SiliconWizard:

--- Quote from: profdc9 on July 29, 2021, 02:55:12 am ---Well, it's been running off my function generator at 3.6864 MHz for about half an hour now, so it seems to be stable at this frequency.

Maybe it is the slight overclocking...

--- End quote ---

That's interesting! I admit I have never tried overclocking Z80 CPUs, so I have no clue how amenable to this they were. Apparently, not very.
Now as cooling the CPU seems to help, you could just add some heatsink on the CPU and call it a day.

woofy:

--- Quote from: profdc9 on July 28, 2021, 10:12:04 pm ---Well, I am slightly overclocking a Z80B to 7.3728 MHz (from 6 MHz).   Perhaps this is marginal.  I am acquiring a 8 MHz version. 

--- End quote ---

The DART runs from the same clk as the CPU, so make sure you have an 8MHz DART too.

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