Truthtables, Karnaughdiagram, PSPICE and a pulsating code.

Thread Starter

Digifan

Joined Oct 25, 2012
1
So im trying to create a circuit that pulsates a code in binary.
I've done a truthtable and done some karnaugh diagrams so I know what kinds of gates etc. to use.
The circuit consists of five 7474's and alot of gates.

Things are working out just fine but for some reason the PSPICE simulator gives me some wierd output, everyhing starts out fine, the five signals are low but when they are supposed to change they are unknown(they become double red lines in the simulator).

Im adding pictures of the error aswell as the circuit.

Any help at all will be greatly appretiated, cause I have no idea what's wrong.

Best regards
Digifan
 

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JoeJester

Joined Apr 26, 2005
4,197
Things are working out just fine but for some reason the PSPICE simulator gives me some wierd output, everyhing starts out fine, the five signals are low but when they are supposed to change they are unknown(they become double red lines in the simulator).
Your diagram is difficult to read.

Q0 is always low and will never change state. Is that your intention?
 

takao21203

Joined Apr 28, 2012
3,696
Maybe you did not consider propagation delays, setup time, dynamic behaviour etc.

Not knowing what your circuit is supposed to do, as well the schematic is incomplete.

Did it work before you optimized it using Karnaugh table?

You have to slice it into independent pieces and make them work correctly step by step.
 
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