Specifications

242 Appendix B— Device Pin Types
device. On subcircuit devices, the simulator must make several passes
through all circuit levels that may affect the value of the signal or may be
affected by it. Setting a pin on a subcircuit device to be an input or output
greatly reduces this overhead.
Output Pins
If a device pin will be used exclusively to drive the attached signal, and the
device cannot be affected by changes in value on the pin, then it should be an
output type. Changes in the value of a signal attached to an output pin do not
cause the device model to be called for reevaluation. This is particularly sig-
nificant for subcircuit devices.
Input Pins
Pins with an input type setting can never place a drive value on the attached
signal. On subcircuit devices, this provides an important hint to the simula-
tor that internal value changes on the attached signal will not affect any
other circuit level.
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