Some
of the things we've worked on are listed below:
Non-Linear Controlled Sources (extension):
Names: arbitrary voltage source, arbitrary current source
category: virtual: voltage sources and virtual: current sources
We have implemented If then else expressions and direct digital
and logical expressions.
Here are some examples:
B1 nplus nminus V = if(v(2) > v(1), 5, 0) // comparator,
pspice syntax
B2 nplus nminus V = v(2) > v(1) ? 5 : 0 // comparator, ISspice
syntax
B3 nplus nminus V = !(v(2) & v(1)) // nand gate
B4 nplus nminus V = (v(2) > v(1)) \ (v(2) > v(3)) // '\'
is the logical or
These types of expressions can be used for sophisticated modeling
within your circuits. I've included more details on these expressions
and operators at the end of this article.
Virtual
table
The "table"
output from a simulation was previously a memory hog.
We didn't notice this until a customer ran a transient
simulation that generated hundreds of thousands of time
points and generated a table containing data from 11 signals,
which resulted in the program crashing. To fix the problem,
we developed a "virtual" table that only stores the data
that is shown on the screen. It now takes up very little
memory. By the way, there is a second way to view the
graph of simulation results as a table. Click on the leftmost
button in the toolbar when the graph is active, and it
converts the view into a table view. This table view shows
the index signal data next to each signal's data, and
it does not synchronize the rows to a shared index signal,
which is why I prefer the separate table window. Also,
you can generate a table from a graph by going to the
graph's special menu and choosing "Create graph from table".
Large
netlists
Most of you probably don't
run simulations from netlists, but for those of you that
do, the netlist window now supports netlists that are
greater than 32K. This was an embarrassing bug to find,
but it's fixed now. Also, in case you do use netlists,
add a line of the following form to automatically generate
a graph and plot v(1) and v(2) when you run the simulation.
.plot tran v(1) v(2)
Speed with
large PWLs
Large PWL
voltage sources used to be slow to edit and circuits with
them used to be slow to run. We have improved the code
so that you can have PWL sources with hundreds of thousands
of data points with wait times of only a few seconds.
In case you didn't know, you have a text file of two columns
of data for time and voltage, you can load it directly
into a voltage source.
Graph signal
vs another signal (instead of vs. time)
Now you can
change the x-axis for a signal, which is useful for I-V
curves or eye-plots. To get to this option, go to the
Edit Plots panel using the button of that name on the
left side of the screen, then choose the Edit Plot page
if it isn't already active, then select the plot whose
y-axis you want to change in the list-box at the top,
then choose its x-axis from the list of graph signals
in the X-axis signal combo-box. Originally in v5.1.5,
this did not work just right. The signal's data points
were being reordered to make the x-axis's data go from
low to high. This problem has been corrected
User defined
parameters
Did you know
that you can set global variables and then use them within
expressions for part parameters. For example, if you had
two resistors that you wanted to keep in a 2 to 1 ratio,
you could define the resistance of one as 2*R, and the
other as R. Then define R as a user-defined parameter
using the menu item by that name in the Schematic's Edit
menu. You can also sweep that parameter when setting up
a sweep of transients, for example. We have now added
the capability to also vary it as a Monte Carlo parameter.
Y-Axis
title reflects the current plot
You can now
specify that the axis' name is the same as that of the
selected plot. To get to this option, go to the Edit Axes
panel using the button of that name on the left side of
the screen, then choose the Left Axis from the Select
Axis combo-box, then choose the Title page below, then
check the Use Selected Signal checkbox
Persistence
of axis settings upon "next" run
Have you ever
zoomed in on an interesting portion of a plot, then changed
a parameter and re-run the simulation and been frustrated
that the graph rescales to fit the new plots. You can
now force the axes to be persistent with a checkbox named
"keep persistent" in the Scale page of the Edit
Axes panel.
Show zero
crossings
Show zero
crossings for a plot on the graph now interpolates to
find an approximation of the zero crossing, rather than
showing the closest generated point.
Cross-Probing
We spent a
lot of time testing and fixing and retesting voltage and
current probes. There were problems in v5.1.5 and earlier
in some extreme cases, and some of these problems even
caused crashes.
Did you know that you can add probes to the schematic
before or after a simulation is done, and it adds the
corresponding plots to the front-graph. If you later delete
the probe, the corresponding plot(s) get deleted. This
works for families of swept or Monte Carlo plots also.
And it also works if the front "graph" is actually
a table.
More notes
on If-Then-Else (ITE) expressions
Within the
ITE condition, change nothing... except fix up operator
precedence bug, and add exclusive-or.
Logical operators supported: &: and
|: or
#: xor
!, ~, ': not
Comparison
operators:
>, <,
= for greater than, less than, and equal.
These ITE
expressions can be nested, e.g.
If((v(1) > v(2)) & (v(1) > v(3)), v(1), if(v(2)
> v(3), v(2), v(3))) // pspice syntax
((v(1) > v(2)) & (v(1) > v(3))) ? v(1) : (v(2)
> v(3)) ? v(2) : v(3))) // isspice syntax
Will return the maximum of v(1), v(2), and v(3)
More notes on logical and digital expressions outside
of the ITE
Comparison operators: >, <, =.
These take real inputs and generate logical (0,1) outputs.
Digital
Operators:
&: and
|: or
#: xor
!, ~: not
These take real analog inputs, convert them to digital
signals and perform the operation, then convert the outputs
back to analog again. The conversions from digital to
analog, and back from digital to analog, use the parameters
in the digital simulation options (bb_ad* and bb_da*)
for threshold levels and for high and low voltages.
e.g. v(1) & v(2) // will return 5V (bb_daOutHigh)
if both v(1) and v(2) are greater than 2.5V (bb_adInHigh),
else return 0 (bb_daOutLow).
Logical
operators: (THIS IS NEW)
These take
logical inputs (0,1) and generate logical outputs (0,1).
' : invert (this is the apostrophe that's with the quotation
mark)
$ : and
\ : or (backslash, not division symbol)
@ : exclusive-or
e.g. (v(1) > 0) $ (v(2) > 0) // will return 1
if both v(1) and v(2) are greater than 0, else return
0.
