Re: Probably stupid problem...

[John Coppens]

On Mon, 23 Sep 2002 15:52:17 -0700
Steven Rubin <address@hidden> wrote:

> 
> >I'm a first time user of Electric and made a very simple circuit with
> >three JK FFs. I connected the JKs of the first to PWR, and the
> >JKs of the second to the Q of the first. The JKs of the third
> >go to an AND of Q0 and Q1. I believe this is the standard connection
> >for a sync counter. Clocks are common.
> >
> >When simulating though, only the first JK acts normally (div 2).
> >
> >I've tried to connect the PRESET and CLR to 1 and 0 etc. I guess I'm
> >missing something very basic here...
> 
> The implementation of FlipFlops is not complete in the built-in ALS 
> simulator.  This is why some of them don't respond under simulation.  Check 
> the VHDL and the netlist code to see more.

Hi Steven.

I checked the simulator routine - it doesn't take into account the PRESET
and CLEAR inputs. It _does_ seem to try and simulate the normal behaviour
of the FF though.

I did a simpler circuit with only two FFs. The second has JK hanging from
the previous one's Q output. This should give a divide-by-4 circuit. I'm 
guessing
there's something wrong with the order of the evaluation of things. I'm
guessing that for some reason the second JK always sees 1 on at least one
of the inputs.

Anyway - after a bit of experimenting something else went wrong: I get a 
message:

  Cannot find VHDL for test

When trying to run ASL sim. Where did that come from?

John

> 
> >I've installed IRSIM, and find I can't define a clock signal? How can I
> >excite a circuit?
> 
> There is an IRSIM "c" command that cycles a particular signal up and 
> down.  You can enter this from the "command line" or by placing it into a 
> "cmd" file.  Alternatively, you can toggle things by hand (the hard way).
> 
> >Also, the time scale in IRSIM is very short - ns or thereabouts. How to 
> >change
> >that? The horizontal scrollbar on the time bar only changes to the left,
> >it's right side is locked in the middle of the range and doesn't move.
> 
> You can fix it in the code, or you can simply zoom out once the window 
> appears.  Use the same commands to zoom the waveform viewer as you do for 
> circuits (Window/Zoom Out).
> 
> >When loading a library, by default the home directory appears. If one tries
> >to change directory by modifying the path, without a filename, Electric
> >hangs...
> 
> No, don't change the path field.  That tells Electric where to find its 
> needed library files.  There should be some UNIX way to set the default 
> directory, but I don't know what it is.
> 
>       -Steven Rubin
> 
> 
> 
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