Re: PSpice Logic Levels

Yep. Basically I needed to create a small state machine to sequentially bring up some circuitry, make some measurements, compare to previous values, act on that, then go back to sleep.

Since I needed to create some clock sources matching the levels and speeds of my wimpy micro-power stuff, I simply created an interface from STIMx, DIGClock, etc, to device level and vice versa, providing me with level and TR/TF adjustability.

I did it in such a way that I can have multiple logic types simultaneously, say PECL and LoV-CMOS, without having to tamper with all that built-in global-power crap.

I've done a lot of chip work for AMCC... a long time ago... the last was some kind of ethernet controller ;-)

They never gave ME a T-shirt :-(

...Jim Thompson

Is there not TR/TF adjustability in the behavioral model with PSpice? That would be strange.

Maybe they knew it wouldn't fit ...

If it's any comfort, only one client ever gave me a company T-shirt. Thanks to those dreaded toploader washers it recently had to be moved to the stack used for "outdoor work and firewood splitting".

On a global level, a not-user-friendly adjustment.

The way I did it, once I figured it out, is down-right child's play, and I can have mixed logic just as easy as just one type.

Be nice ;-)

...Jim Thompson

Hmm, LTSpice allows that on a local level. Initially I just didn't know where to enter it but two people sent me a hint. Usenet is wonderful.

In LTspice I believe you're actually talking pulse SOURCES.

I'm talking digital stimulation, arbitrary strings of 1's and 0's converted to specifiable logic levels and TR/TF.

(PSpice is a "mixed-mode" simulator.)

...Jim Thompson

No, logic blocks. Source parameters can also be set, either by text or via an input window, but I wasn't talking about sources.

I just follow the input with a logic gate such as an inverter and then set TR/TF for that particular gate.

How would you generate 1110101110001011001110001111....?

And then how would you convert 1110101110001011001110001111....

Into 0-to-3.3V CMOS logic with 10ns rise and fall time.

...Jim Thompson

I don't now, my sequences were simpler and I always concocted them out of several pulse sources and some logic. Maybe it can also read from a file, Helmut Sennewald would know that.

That's easy. Follow it with a buffer and set its TR/TF both to 10nsec.

Suppose the logic levels were -1V and +1.5V. How would you do that ?:-)

...Jim Thompson

Simple. Go into the component attribute editor (one right click on the device where you want those levels). Left click on SpiceLine2. Enter this:

Vhigh=1.5_Vlow=-1.0

Hit run, pour glass of Merlot :-)

Not quite, where did you get...

...Jim Thompson

You'd have to ask Helmut, so far my sequences were simple and could be done with 2-3 sources plus some logic. I could probably figure it out but not right now. Got to design a rather unorthodox high voltage circuit, Larkin design process, meaning from CAD straight to fab. One mistake ... phssst ... *BANG* ... sirens wailing ... egg in the face.

I can type "ON" time, "OFF" time, and then the sequence...

A day later you'll still be trying to find the right pulse source arrangement.

As soon as you get it working I'll decide to change the sequence to...

...Jim Thompson

Well, I think the real reason was that they had been asking for a solution to the problem for about two months, and in a couple of days, I had the fix for them. It got them past a big roadblock...

-- Charlie Edmondson Edmondson Engineering Inc

BTW, Jim, I would like a copy of what you've created. Hopefully one of the guys at EMA will see this, and ask for a copy as well... ;-)

-- Charlie Edmondson Edmondson Engineering Inc

Well, maybe LTSpice can read in strings, I just don't know yet. Because I never needed it.

It's in PSpice Schematics format. Is that OK?

...Jim Thompson

It's been fun yanking your chain. NOW go have your glass of Merlot. I'll go open a bottle of Australian Chardonnay ;-)

...Jim Thompson

Nah, got at least 2h of work ahead of me. Then dinner, walking the beasts, bible study, and a nice glass of Sierra Nevada Anniversary Ale.