RE: FLASH ROM incompatibilities with C128

Experience was you could not reliably create minimum delays through gates
as minimum switching times are actually undocumented and some runs could
propagate to an unknown condition very quickly (.5ns)  Since all gates in
a package tend to be equally fast or slow, a delay chain of 4 devices can
have a real-life variation of 2-20ns, very tough to design with, at least
at high qtys.

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Gerrit Heitsch
Sent: Wednesday, December 5, 2012 11:04 AM
To: cbm-hackers@musoftware.de
Subject: Re: FLASH ROM incompatibilities with C128

On 12/05/2012 03:46 AM, Bil Herd wrote:
> The 6502 architecture can suffer in one area in particular with faster
> parts on read cycles and that is at the end of the cycle; Fast parts
> sometimes are faster to release data and let it go invalid.  The '02
> family can require 5-10 ns of hold time which might as well be forever
> if you don't have it.

If that's the case, then all you'd have to do would be to delay the _CS
signal for the Flash through 4 or all gates of 74LS04.

  Gerrit



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