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AR# 19402

6.2i UniSim - Why are there no longer any unit (intrinsic) delays in the UniSim library components?

Description

Keywords: simulation, 100 ps, change, 6.1i

Urgency: Standard

General Description:
Why do the UniSim libraries no longer have the 100 ps of unit delays on them?

Solution

The intrinsic delay of 100 ps was not a true representation of a behavioral model because a true behavioral model should not have any delays from the input to the output. This change provided the following advantages:
- Faster simulation times because there are no longer 100 ps delays to outputs.
- Fixed certain race condition occurrences that were caused by the intrinsic delays.
- Much easier to debug because when the signal changes at the input to a component, the output reflects this change; no longer need to take the extra 100 ps into consideration.

NOTE: These changes only apply to the non-synchronous elements. The synchronous elements have 100 ps of clock-to-out in the ISE 6.2i libraries and above.
AR# 19402
Date Created 09/03/2007
Last Updated 11/18/2008
Status Archive
Type General Article