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Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Looking for the help of some digital experts here (as i am not)
I have a photographic application in which an event will trigger a 4-bit digital counter (i.e. 74161) Is there a simple way to make the count terminate after a single count (0-15)? Sure, i can do it with multiple gates sampling the output and feeding back through gates to the ENA pin of the counter, but i'm trying to do this as simple as possible with as small a number of chips as possible. And without going uProc as well. Needs to be discrete logic.
I guess basically its just a one-shot 4-bit counter i'm looking for.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Do you want to count 15 or 16 events? If it counts from 0 to 15 then you have only counted 15 events.
If you want to count 16 then you can use the above circuit and feed the carry into the enable instead of reset, then it will stop counting after 16 events.
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
Well if he wants it to count from any number otehr then 0 I'd say just load some switches onto a-d and on load, then set it to the desired start # and load the bits, then start teh counter.Aslo I thought about runig it to the enable pin, but then he'd need a lacth with reset, because since its a logic device the CRO pin is always low, untill it counts to 15 then it goes high, so if you fed the CRO pin to enable directly it wouldn't work at all since it has to be held high to run, If you kept the inverter but just sent the output to enable then it would just reset the same as mine does anyways.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Actually it needs to count to 15, but then stop counting until another enable pulse is received. The counter autmoatically resets to zero once it reaches the end.
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
Just for reference I used a display so I could make sure my concept was right, since I was using my simulator. Evr, even though your looking for the fewest parts and simplest setup, this would still be 2 ic's the lacth and the 74161. Heres the counter with a latch.
With this it'll get to 15 and reset, then just hit the reset and it'll start counting again. Unless you already figured that out.
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
It works fine, I tested it on my simulator, , and it works, as for actual part numbers its upto your discretion, the values I used where just what the simulator gave me, I probly could have chosen a different part number but Here it just changes switching speed and such.
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Digital Logic / Counter question
, and it works, as for actual part numbers its upto your discretion, the values I used where just what the simulator gave me, I probly could have chosen a different part number but Here it just changes switching speed and such.