User`s guide

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36 Di
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ital Device Modelin
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Constraint Checker
(CONSTRAINT Primitive)
The CONSTRAINT primitive provides a general constraint
checking mechanism to the digital device modeler. It performs
setup and hold time checks, pulse width checks, frequency
checks, and includes a general mechanism to allow user-defined
conditions to be reported. See the Digital Devices chapter in the
online MicroSim PSpice A/D Reference Manual for more
information.
Setup_Hold
The expressions in the SETUP_HOLD specification may be
listed in any order.
CLOCK defines the node that is to be used as the reference for
the setup/hold/release specification. The assertion edge must be
LH or HL (for example, a transition from logic state 0 to 1 or
from 1 to 0.)
DATA specifies which node(s) is to have its setup/hold time
measured.
SETUPTIME defines the minimum time that all DATA nodes
must be stable prior to the assertion edge of the clock. The time
value must be a nonnegative constant or expression and is
measured in seconds. If the device has different setup/hold
times depending on whether the data is HI or LOW at the clock
change, you can use either or both of the following forms:
SETUPTIME_LO = <time value>
SETUPTIME_HI = <time value>
If either of the time values is 0, then no check is done for that
case.
HOLDTIME is used in the same way as SETUPTIME and also
has the alternate _LH and _HL formats and 0 value condition.
RELEASETIME causes the simulator to perform a special-
purpose setup check. Release time (also referred to as recovery
time in some data sheets) refers to the minimum time that a