Re: How to design non-trivial cartridges for c-64?

From: Jim Brain (
Date: 2007-05-28 04:08:19

Bil Herd wrote:
> The area you have to watch is that the data is valid for only a short
> period after Phi goes low, known as the hold time.  Holdtimes are as
> short as 10-20 ns (shorter if using Phi2) which means that if you have
> too much logic in line to create the strobe, the data goes away before
> the strobe (took you longer than 10ns to decide to do something).  Rule
> of thumb is the strobe has time for only one level of TTL type logic on
> anything trying to capture data.  
So, for something a bit more time intensive, are there any suggestions?  
Delay after Phi2 going Hi to start the work?

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