PSpice User Guide
Digital device modeling
October 2019 409 Product Version 17.4-2019
© 1999-2019 All Rights Reserved.
For a complete list of reference functions and transition functions, see
the Digital Devices chapter in the online PSpice Reference
Guide.
PINDLY
PINDLY contains the actual delay and constraint expressions for
each of the outputs.
The CASE function defines a more complex, rule-based and works as a rule section mechanism for
establishing path delays. Each boolean expression in the CASE
function is evaluated in order until one is encountered that produces
a TRUE result. Once a TRUE expression is found, the delay
expression portion of the rule is associated with the output node
being evaluated, and the remainder of the CASE function is ignored.
If none of the expressions evaluate to TRUE, then the DEFAULT
delay is used. Since it is possible for none of the expressions to yield
a TRUE result, you must include a default delay in every CASE
function. Also note that the expressions must be separated by a
comma.
In the PINDLY section of the PINDLY primitive in the model listing, the
four output nodes (QA_O through QD_O) all use the same delay
rules. The CASE function is evaluated independently for each of the
outputs in turn. The first delay expression is:
CLOCK & LOADBAR=='1 & TRN_LH, DELAY(-1,13NS,20NS)
This means that if CLOCK is TRUE, and LOADBAR is equal to 1, and
QA_O is transitioning from 0 to 1, then the values of -1, 13ns, and
20ns are used for the MINIMUM, TYPICAL, and MAXIMUM
propagation delay for the CLK-to-QA data output of the chip. In this
case, the manufacturer did not supply a minimum prop delay, so we
used the value -1 to tell the simulator to derive a value from what was
given. If this statement is TRUE, then the simulator assigns the
values and move on to the CASE function for QB_O and eventually
RCO_O.
For instances where one or more propagation delay parameters are
not supplied by the data sheet, the simulator derives a value from
what is known and the values specified for the .OPTION
DIGMNTYSCALE and DIGTYMXSCALE.
