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General Form:
pulse(v1 v2 [td tr tf pw per td1 td2 ...] [pattern_spec])
vin 3 0 pulse(-1 1 2ns 2ns 2ns 50ns 100ns)
vin1 1 0 pulse(0 1 2n .5n .5n 1n 0 6n 10n)
v2 4 0 v(1)*pulse(0 1 5n 10n)

This function applies only to transient analysis, where time is the running variable. When referring to default values, tstep is the printing increment and tstop is the final time in transient analysis.

The following are the numerical parameters, the pattern_spec is used to specify a patterned pulse train and the syntax will be described separately below.

parameter description default value units
v1 initial value   volts or amps
v2 pulsed value   volts or amps
td delay time 0.0 seconds
tr rise time tstep seconds
tf fall time tstep seconds
pw pulse width tstep seconds
per period tstop seconds

The signal starts at value v1 at time=0. At time td, the pulse begins, the value arriving linearly at v2 after the rise time tr. The value v2 is maintained for the pulse width time pw, then reverts linearly to value v1 over the fall time tf. If a period per is given and nonzero, a periodic train of pulses is produced, starting at td, with the second pulse starting at td+per, etc. The minimum value for per is tr+tf+pw, which is silently enforced.

Numbers td1, td2, etc. following per are taken as additional delay values (similar to td) and a pulse will start at each given value. These will actually be superposed periodic pulse trains if per is nonzero (it must be given in any case when using the additional delays).

A single pulse so specified is described by the following table:

time value
0 v1
td v1
td+tr v2
td+tr+pw v2
td+tr+pw+tf v1
tstop v1

Intermediate points are determined by linear interpolation. It is not an error to omit unused parameters, for example the specification

vxx 3 0 pulse(0 1 2n 2n)
describes a voltage which, starting from 0, begins rising at 2 nanoseconds, reaching 1 volt at 4 nanoseconds, and remains at that value.

If this function is used bare and not part of an expression in a voltage or current source, then the general source instance parameters prm1 etc. map as below. It is possible to read and alter these values using the special vector @device[param] construct, or with the alter and sweep commands. However, there is no sanity checking so bad numbers can cause wild behavior or worse.

prm1 v1
prm2 v2
prm3 td
prm4 tr
prm5 tf
prm6 pw
prm7 per

next up previous contents index
Next: Pattern Generation Up: Tran Functions Previous: Interpolation   Contents   Index
Stephen R. Whiteley 2022-09-18