Specifications

Device Simulation Characteristics 69
Device Simulation Characteristics
Device and Pin Delay
This section describes how to set delay values for primitive devices, subcir-
cuit devices, and pins.
Primitive Device Delay
Primitive devices (e.g., those with a program–defined simulation model)
have a single delay value which can be set to any integer value from 0 to
32,767. This delay is applied when any input change causes any output
change. In addition, a pin delay in the range 0 to 32,767 can be set on any
input or output pin. Pin delays can be used to set arbitrary path delays
through the device. More information on pin delays follows.
The initial delay value is set to 1 when the device is created, but this can be
changed later using the Simulation Params command. This delay applies
whenever any input change causes an output change. There is no provision
in the built–in simulation models for different delay values on low–to–high
and high–to–low transitions. The Clock and I/O devices have no delay
characteristic. See the following notes on delay in subcircuit devices.
Subcircuit Device Delay
Subcircuit devices inherit their delay characteristics from their internal cir-
cuit and have no “device delay” characteristic of their own. The Simulation
Params command cannot be directly used on a subcircuit device, although
pin delays can be set separately on each instance of a subcircuit device to
customize path delays.
Pin Delays
Any input or output pin on any device (including port connectors and sub-
circuit devices) can have a pin delay associated with it. Pin delays normally
default to 0 time units, but can be in the range 0 to 32,767.
LW Reference.bk Page 69 Monday, December 15, 2003 5:59 PM