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Count 1s in PROM

Sudd

Oct 7, 2017
3
Joined
Oct 7, 2017
Messages
3
Hey!

I'm trying to design a circuit that counts 1s in a 16 cell 4 bit PROM.

I have a counter that counts from 0-15 that adresses the PROM. It counts up a step for every 4th clock pulse. 4 bits per up count comes out of the PROM, goes through a parallell to serial shift reg and then into decade counters. The result should be presented in BCD.

It works all fine, until the very end. It wont count the last cell in the PROM.

Please help!
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Recall that the count starts at 0 and ends at 15, not from 1 to 16
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Yes, but is your circuit registering the FIRST location (0000) since you state that it requires 4 clock pulses to get to the first P/S shift output.

Upload your schematic.
 

Sudd

Oct 7, 2017
3
Joined
Oct 7, 2017
Messages
3
Yes, but is your circuit registering the FIRST location (0000) since you state that it requires 4 clock pulses to get to the first P/S shift output.

Upload your schematic.

Here's what it looks like. For every fourth clock pulse 4 new bits are sent to the P/S shift. The 0-15 counter disables itself when it gets to 15 (RCO connected to enable).
 

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