Flip-Flop Orcad Pspice Simulation

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pspice flipflop

Hello All,

I am new to this forum as well as Orcad.

I having some problems simulating a Flip-Flop ( 74LS74 from the psice lib)

When running the simulation I can see the alternating digital output from dstm into the clk of the flip-flop but when monitoring the D Q and QBar of the flip-flop all I see is three red flat lines ie no digital output.

If anyone could help explain how to implement this or even point me to a good tutorial / guide that would be great as I have googled this to death ;-)
I have purchased some books for Orcad from Amazon but am awaiting delivery.

I have uploaded two images, one of the capture and the other of the ocilloscope (pspice simulation)




TIA
SRG
 

Give power supply and ground

u give D to VDD and see the output first

u see output file it will have the clear error message
 

Hi,
I am also facing the same problem by getting straight lines.
I think u must have finished analysing the outputs,
Could any one can help me..


Thanks in advance
 

The FF state is unknown, because no initial condition or reset signal is applied.
 

you have to define the initial status for the flipflops

In Analysis --> Setup --> Digital Setup you may see FlipFlop Initialization marked as All X. Change the value to All 0 or All 1 and see if you can now simulate it.
 

Clear and preset should be high if you want to clock it.

Keith
 

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