Re: high level on different 6502

From: Segher Boessenkool <>
Date: Sat, 5 Nov 2016 18:04:33 -0500
Message-ID: <>
On Sat, Nov 05, 2016 at 10:01:31PM +0100, Francesco Messineo wrote:
> the High voltage at 2.5V isn't  a problem in itself (if it keeps the
> level when loaded). TTL logic real "bad" noise margin is on the low
> level (0.5V max output vs 0.8V max input).
> So in theory 2.5V High should work as it has a still better noise
> margin than the correct Low levels. Look also at the actual Low level
> voltages on these parts however.

The 6502 datasheet says output high is at least 2.4V.  The RIOT (6532)
datasheet says input high is at least 2.4V.  If the outputs can only
reach 2.5V then they will be slow ramping up to 2.4V, as well.

> Then, one might wonder if Synertek parts were always marginal or they
> didn't age well, but I can't surely tell :)

Did you measure it with any (external) load?


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Received on 2016-11-06 00:00:02

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