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From: Keith Wootten
Subject: Re: One and only one pulse gate.
User-Agent: Turnpike/6.02-U (<7r9OMDU2ooRJCQmjnYJxyjtHfm>)
X-Inktomi-Trace: pc2-rdng1-6-cust50.winn.cable.ntl.com 1039630575 28227 126.96.36.199 (11 Dec 2002 18:16:15 GMT)
Date: Wed, 11 Dec 2002 18:15:55 +0000
NNTP-Posting-Date: Wed, 11 Dec 2002 18:16:16 GMT
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In message <firstname.lastname@example.org>, Tiger Phil
>I need to incorporate a gate in a TTL circuit that will only allow one
>and only one pulse in a pulse stream to go to the next stage. It must
>also be able to be reset manually(bounceless switch, etc.)
Assuming your pulse is lo-hi-lo, here's a simple way:
It's the hi-lo transition which needs to lock out subsequent pulses, so
start with your input signal connecting to the clock input of a negative
edge triggered D-type. Tie D Hi and connect Qbar to one input of an And
gate. Connect your input signal to the other And input and use the And
output as your one-shot signal.
Connect push button to Hi (with pull-down) to the active Hi clear input
of the D-type.
Push button, D-type is cleared taking Qbar Hi (and Q Lo) which allows
And to pass signal through. Negative edge on signal clocks D-type
setting Q Hi and Qbar Lo which locks out signal through And until reset
by push button.
As for actual chips, I dunno, see what's in the box. You may have an
active Lo clear on the D-type.
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