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one shots

Posted: Fri Oct 16, 2009 11:40 am
by billw
Is there any way to implement a one-shot delay?

Re: one shots

Posted: Mon Oct 19, 2009 3:11 pm
by admin
There are no delays per se, but gates get evaluated in same way as real signal will be spread. That means that if you need to have your signal delayed you can add two inverters and they do the trick.
However this technic is not reliable both in the program itself as well as in the real life circuit. You’d better try to find a logical solution for your problem. If you can share what you are trying to achieve we can think about it together.

Re: one shots

Posted: Thu Oct 29, 2009 6:22 am
by billw
Eugene,

Thanks for the response!!
I have implemented one-shots using counters. It is a count to n and stop. A positive input trigger clears the counter and starts counting clock pulses until the desired count is reached and it stops and outputs a positive transition. This of course, requires that you carefully consider the over all timing scheme if clocking is required for other circuits. I have made re-triggerable and non re-triggerable circuits. I will try to find a place to upload them so I can share them.

It would still be nice to have some type of user defined delay elements to substitute for r/c charging schemes used in many circuits (i.e. power on resets, oscillators, multi-vibrators, watchdog timers, etc.) that must be independent of the master clock. Perhaps you can consider this for a future version.

Thanks Again,
Bill

Re: one shots

Posted: Thu Oct 29, 2009 8:27 am
by admin
Hi Bill,
You can upload your circuit right here or create a new topic.
Thanks,
Eugene

Re: one shots

Posted: Fri Oct 30, 2009 8:51 am
by billw
Here is a circuit for a 4 bit programmable re-trigerable one shot. It can be expanded by adding more timer elements and expanding the NAND gate (see drawing). Each timer element consists of 1 D flip flop, 1 JK flip flop and 1 exclusive NOR gate.
1. Apply the bits to each element (MSB on top)
2. Load the bits into the elements by applying a positive transition on the Load pin.
3. Start the timer by applying a positive transition to the Trig pin.
4. The one shot will time out when a count of n-1 has been reached (a value of 9 will give a 8 clock cycle pulse)
5. Enjoy!

Re: one shots

Posted: Fri Oct 30, 2009 11:32 am
by admin
Thank you for your wonderful contribution. Can you also upload the project file itself so people will just need to copy/paste what they want?
:D

Re: one shots

Posted: Fri Oct 30, 2009 2:20 pm
by billw
Eugene,

How do I upload projects? I can't seem to upload a circuitproject file as an attachment.

Bill

Re: one shots

Posted: Fri Oct 30, 2009 4:05 pm
by admin
Sorry, this extension was not allowed. I’ve enabled it. Can you please try again?

Re: one shots

Posted: Sat Oct 31, 2009 5:26 am
by billw
Here is the project file