one shots

[billw]

Is there any way to implement a one-shot delay?

[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.

[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

[admin]

Hi Bill,
You can upload your circuit right here or create a new topic.
Thanks,
Eugene

[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!

[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?

[billw]

Eugene,

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

Bill

[admin]

Sorry, this extension was not allowed. I’ve enabled it. Can you please try again?

[billw]

Here is the project file