Re: Looking for a VHDL forum or individual help

From: Groepaz <>
Date: Mon, 23 Aug 2010 20:22:18 +0200
Message-Id: <>
On Montag 23 August 2010, you wrote:
> On Mon, 23 Aug 2010 wrote:
> > Regarding the model, it is in fact based on my TTl6502. And Gideon
> > couldn't detect any flaw :) Using this model I discussed my finding
> > that IMHO all the cores I know, including Gideon's, treated NMI as
> > level triggered. The docs state that the NMI in the 6502 is edge
> > triggered. He agreed with my findings. But so far it never caused
> > problems, so why changing it? I gave him an example where things
> > could go wrong. Anyway if the docs state edge triggered, why not
> > implementing it?
> How would the NMI even work if it is implemented as level triggered?
> It's _non_ maskable.  If strictly level triggered it will just endlessly
> retrigger the interrupt with no chance to ack, no?

and thats what happens actually, and its why there is a RC element wired to 
the restore key :)


A 'hacker' is any person who derives joy from discovering ways to circumvent 
<Robert Bickford>

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Received on 2010-08-23 19:00:40

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