LT Spice...some questions

Just downloaded LT Spice, and it's a great program, specially
for the cost.
However, I seem to have a lot of trouble with the graphing
system. The X axis seems to have a mid of its own. Sometimes it
refuses to rescale, other times it repeatedly reverts back to its
randomly chosen default scale. The Y axis seems to behave fine.
It can get the net names confused, like calling "output" by
"net002" and "net002" by "net003".
When I identified net "output" as port type "Output" the
circuit stopped working until I undid it. What happened there?

 

[Mike Engelhardt]

Ratman,

However, I seem to have a lot of trouble with the graphing
system. The X axis seems to have a mid of its own. Sometimes it
refuses to rescale,

It zooms whenever you drag a box over the plot. Note you can
undo/redo zooms as well as anything else. However, if you resim,
the X axis will usually not allow you to plot beyond the extent
of the data. For example, if you have .tran from 0 to 100us,
you can't plot from -10us to 200us.

The Y axis seems to behave fine. It can get the net names
confused, like calling "output" by "net002" and "net002" by
"net003".

No, it doesn't get names confused, but it does allow you to
short two nets together. It will pick one of the two names
to use.

When I identified net "output" as port type "Output" the
circuit stopped working until I undid it. What happened
there?

Pilot error. It does nothing with the port type, except notice
that maybe you need to identify it as a port for hierarchical
reasons.

--Mike

 

OK, found the X axis problem...X axis always defaults back to
..tran on a new run. Makes sense.
Found the net name problem. You can't just name the net, the
name box must be attached to the wire as well. The program can get
confused and run a wrong net (maybe).
Thanks, all better for now. This is my first adventure with
spice so I will probably have more simple questions.



On 01 Feb 2004 23:41:46 EST, "Mike Engelhardt" <pmte@concentric.net>
wrote:

Ratman,

However, I seem to have a lot of trouble with the graphing
system. The X axis seems to have a mid of its own. Sometimes it
refuses to rescale,

It zooms whenever you drag a box over the plot. Note you can
undo/redo zooms as well as anything else. However, if you resim,
the X axis will usually not allow you to plot beyond the extent
of the data. For example, if you have .tran from 0 to 100us,
you can't plot from -10us to 200us.

The Y axis seems to behave fine. It can get the net names
confused, like calling "output" by "net002" and "net002" by
"net003".

No, it doesn't get names confused, but it does allow you to
short two nets together. It will pick one of the two names
to use.

When I identified net "output" as port type "Output" the
circuit stopped working until I undid it. What happened
there?

Pilot error. It does nothing with the port type, except notice
that maybe you need to identify it as a port for hierarchical
reasons.

--Mike