PSpice: Possibility to initialize flipflops randomly

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.]

On Mon, 10 Nov 2008 02:17:35 -0800 (PST), norbert.notz@gmx.de wrote:

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

 

On 10 Nov., 17:07, Charlie E. <edmond...@ieee.org> wrote:

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]

<norbert.notz@gmx.de> schrieb im Newsbeitrag
news:704b30ac-0ccd-4025-a72f-055560898448@q26g2000prq.googlegroups.com...
On 10 Nov., 17:07, Charlie E. <edmond...@ieee.org> wrote:

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

 

[Jim Thompson]

On Tue, 11 Nov 2008 19:59:42 +0100, "Helmut Sennewald"
<helmutsennewald@t-online.de> wrote:

norbert.notz@gmx.de> schrieb im Newsbeitrag
news:704b30ac-0ccd-4025-a72f-055560898448@q26g2000prq.googlegroups.com...
On 10 Nov., 17:07, Charlie E. <edmond...@ieee.org> wrote:
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

If your circuit can exhibit untoward behavior during a random start I
usually design so that the desired sequence can be reached in a few
clock cycles, or include a RESET sequence in the state machine.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food

 

[Jim Thompson]

On Mon, 10 Nov 2008 02:17:35 -0800 (PST), norbert.notz@gmx.de wrote:

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.

I think .IC will work with the digital.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food

 

... 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.

 

... 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.

 

[Jim Thompson]

On Thu, 13 Nov 2008 23:34:25 -0800 (PST), norbert.notz@gmx.de wrote:

... 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.

Yep. I'm with you. It's hard, sometimes, to convince yourself that
you haven't missed a lock-up state ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food