eldo_user

Specifying Simulation Output
X-Axis of Waveforms
This is used as a precursor to VDIG to plot an analog curve as digital with reference to
any stated threshold voltage(s).
• VTH[1]=VAL
If a voltage threshold is specified, the bus of an analog signal is plotted as a bus
(hexadecimal format), else all the different signals of the bus are plotted separately in
the waveform viewer as analog waves. (VTH and VTH1 are equivalent to ensure
backwards compatibility.)
• VTH2=VAL
This can be used to plot the indeterminate value as shown below:
o
o
When only VTH1 is given: If value < VTH then logic state 0. If value > VTH then
logic state 1.
When both VTH1 and VTH2 are given: If value < VTH1 then logic state 0. If VTH1
< value < VTH2 then state X. If value > VTH2 then logic state 1.
Related Topics
Tip
See “.DEFPLOTDIG” in the Eldo Reference Manual.
X-Axis of Waveforms
Plotting, Printing and Probing
X-Axis of Waveforms
In general, the created waveforms have their X-axis implicitly defined by the corresponding
analysis. For example, the X-axis of a transient waveform is time, the X-axis of an AC
waveform is frequency, and so on. The X-axis for a transient waveform is defined by the
.TRAN tstep tmax command, it ranges from t=0 to t=tmax. The X-axis for an AC waveform is
defined by the frequency points in the .AC command. DC and NOISE waveforms also inherit
their X-axis from the corresponding analysis command (.DC or .NOISE).
For all analyses but the transient analysis, the X-axis range and the spacing of points in the
X-axis are thus predictable. For example, the frequency points in a .AC command are either
listed explicitly or regularly spaced, in a predictable way. For transient analysis however, this is
different. Eldo always uses a variable timestep algorithm, and the spacing of the timepoints
where the circuit is solved is dictated by accuracy considerations only (see the Speed and
Accuracy chapter). Thus the total number of timepoints is generally not predictable. By default,
all computed timepoints are stored in the binary output files, so that any rapid change or glitch
can be inspected visually in the waveform processor.
However, when working with large circuits and/or long transient simulations and/or storing
many waveforms, this may generate huge output files. The loading and post-processing of these
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Eldo® User's Manual, 15.3