User`s guide
Probe Trace Expressions 17
-57
Di
g
ital Trace Expressions
Digital output variables in Probe vary from those used in
PSpice A/D analyses as follows:
• Digital net values are specified by:
<digital net>[;display name]
as opposed to the <digital net> format used by PSpice A/D.
With this format, the digital signal can be displayed on the
digital plot with an optional alias.
• The output from several digital nets can be collected into a
single output of higher radix known as a bus.
A bus is formed by enclosing a list of digital net names
(separated by blanks or commas) within braces according to
the format:
The elements of the bus definition, taken left to right,
specify the output values of the bus from high order to low
order.
By definition, a digital signal is any digital net value or a logical
expression involving digital nets. For the digital output variable
formats described earlier, you can use a digital signal expression
everywhere a net name is expected. You can also form buses
into expressions using both logical and arithmetic operators.
As a result, the generalized form for defining a digital trace is:
<digital trace expression> [;display name [;radix]]
{<high-order net> [mid-order net]* <low-order net>}
This
placeholder...
Means this...
digital trace
expression
expression of digital buses or digital
signals.
display name
name that will be displayed on the screen;
if no display name is specified, the actual
trace expression is used; if a display name
is given, it is available for use in
subsequent trace definitions.
For a procedural discussion of
di
g
ital trace expressions, see
Analyzing Results on
page 14-23 in the Digital
Simulation
chapter.
Example: You can request that
four bus lines be displayed
to
g
ether as one hexadecimal
di
g
it. You can combine up to 32
di
g
ital si
g
nals into a bus.
Example: { Q2, Q1, Q0 }
specifies a 3-bit bus whose hi
g
h-
order bit is the di
g
ital value at net
Q2.
Exception: You can display your
radix desi
g
nation option with the
di
g
ital trace expression by
leavin
g
the display name blank
and usin
g
the followin
g
syntax:
di
g
ital trace
expression
;;
radix