Re: Weird /KERNAL line on old boards

From: Jim Brain <brain_at_jbrain.com>
Date: Tue, 10 Jul 2018 13:43:26 -0500
Message-ID: <549911e3-9639-96e0-1075-ea75ff7e52ed@jbrain.com>
On 7/10/2018 12:54 PM, silverdr@wfmh.org.pl wrote:
>
>> On 2018-07-09, at 00:59, Nejat Dilek <imruon@gmail.com> wrote:
>>
>>> Or require a longer _KERNAL pulse than this false pulse?
>> How? I use this pulse to interrupt an attiny85. Even if I check for
>> the signal again in the interrupt it's all open to every kind of race
>> conditions since this false signal pops up quite randomly (unless
>> tamed) before and/or after intended access.
> As long as the assumption is that valid pulse is always longer than the longest spurious one, you can use the "software debouncing" - similar to what is sometimes used to debounce relatively fast switches, without adding significant capacitance, Schmitt triggers, etc. I used it more than once with good results.
I think it will require moving from an interrupt driven approach on the 
AVR (used now), to a polling approach:

while(PINC & _BV(PIN5)) {} // or whatever
if(!(PINC & _BV(PIN5)) {
  // real signal.
}

An instruction on the 16MHz AVR takes at least 62.5nS, so the next 
comparison will push you beyond the 42nS issue.
Received on 2018-07-10 21:01:47

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