Joined: Sep 26, 2016 Posts: 134 Location: norwich, uk
Posted: Wed Apr 04, 2018 4:19 am Post subject:
latching logic puzzle
Hi,
I need a 2 input, 1 output gate that does the following:
Output is low unless both inputs are high (like '&')
but stays high until BOTH inputs go low.
Some sort of flip flop or latch thing I recon but I havent as yet come across one that does the job.
Thanks!
(I feel like im constantly writing little questions here to try and solve my lunetta problems, feel free to politely ask me not to if it is annoying!) Last edited by mike page on Fri Apr 06, 2018 12:19 am; edited 2 times in total
It can probably be done simpler ... but when you'd use an SR flipflop you could SET it with the AND of the two inputs and RESET it with the NOR of those same inputs.
And, let me kindly ask you to please keep asking questions :-) _________________ Jan
also .. could someone please turn down the thermostat a bit.
Joined: Sep 26, 2016 Posts: 134 Location: norwich, uk
Posted: Wed Apr 04, 2018 7:17 am Post subject:
That is an elegant little solution!! Love it!
will it send a second pulse as input c gets triggered?
maybe a cap and resistor on the output could solve this if its an issue.
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
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Posted: Thu Apr 05, 2018 2:29 am Post subject:
yes, when one of the inputs goes low it is the equivalent of a piece of wire attached to itself. A small capacitor could work
but it wil be discharged by whatever you attach the output too so it needs to be big enough but also small enough to handle
the frequency. I think the 4051 is just a better options and because both halves of the 4052 share the control inputs
it's probably not that useful anyway.
Joined: Sep 26, 2016 Posts: 134 Location: norwich, uk
Posted: Thu Apr 05, 2018 3:27 am Post subject:
PHOBoS wrote:
I think the 4051 is just a better options and because both halves of the 4052 share the control inputs
it's probably not that useful anyway.
exactly. I was thinking I could probably use it to get a sort of inverted output, but I dont have a use for that in the thing im designing so the 4051 is probably the way to go. Cheerzz
Just saw this thread and I would do it just like Blue Hell and SteveG said. It can be done with just one quad NAND IC (4011 or 4093) if you use one NAND to set and the wired-OR to reset the RS-FF from two NANDs.
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