PSpice: Possibility to initialize flipflops randomly

[[email protected]]

Hi.

I'm currently working on a simulation of a digital circuit. In order
to find out if I really need power-up resets for all flipflops I would
like to perform some simulations with random initial states.

Can PSpice do this automatically? I only can find an option to switch
between 0, 1 and X state as inital state for ALL flipflops.


Regards,
Norbert N.

 

[Charlie E.]

Hi.

I'm currently working on a simulation of a digital circuit. In order
to find out if I really need power-up resets for all flipflops I would
like to perform some simulations with random initial states.

Can PSpice do this automatically? I only can find an option to switch
between 0, 1 and X state as inital state for ALL flipflops.


Regards,
Norbert N.

Sorry Norbert, but those are the options. Usually, you should use
'X', as this basically says that, until the FF is TOLD what state it
should be, it doesn't have a state. Most set them all to 0 or 1,
(usually 0) to not have to go through the trouble of initializing
everything.

Charlie

 

[[email protected]]

Sorry Norbert, but those are the options.  Usually, you should use
'X', as this basically says that, until the FF is TOLD what state it
should be, it doesn't have a state.  Most set them all to 0 or 1,
(usually 0) to not have to go through the trouble of initializing
everything.

Charlie

Thanks for your response Charlie.

I know that I can force all FFs to 0 or 1 default state in order to
simplify the simulation circuit.

But I want to find out if I need initial resets in the REAL circuit
where I have to expect random initial FF states.

 

[Helmut Sennewald]

Sorry Norbert, but those are the options. Usually, you should use
'X', as this basically says that, until the FF is TOLD what state it
should be, it doesn't have a state. Most set them all to 0 or 1,
(usually 0) to not have to go through the trouble of initializing
everything.

Charlie

Thanks for your response Charlie.

I know that I can force all FFs to 0 or 1 default state in order to
simplify the simulation circuit.

But I want to find out if I need initial resets in the REAL circuit
where I have to expect random initial FF states.


Hello Norbert,

This will require that you set every possible combination as a start
condition.
It's useless to rely on what a programmer of PSPICE has decided for the
default at startup.

Best ergards,
Helmut

 

[[email protected]]

... usually design so that the desired sequence can be reached in a few

clock cycles ...

Sure! I also did so and it looks like it works. I also wanted to find
a comfortable way to verify that.

 

[[email protected]]

... usually design so that the desired sequence can be reached in a few

clock cycles ...

Sure! I also did so and it looks like it works. But I wanted to find
a comfortable way to verify that.