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

From: André Fachat (
Date: 2007-05-28 14:26:46

> 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?

You can delay the data by feeding it through a buffer (e.g. 74ls245) first.


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