Answers Database
XPLA Professional: Timing simulation gives different results than simulation with the *.vho or *.vo file.
Record #7524
Product Family: Software
Product Line: CoolRunner
Product Part: XPLA Fitter
Problem Title:
XPLA Professional: Timing simulation gives different results than simulation with the *.vho
or *.vo file.
Problem Description:
Urgency: Standard
General Description: Why does the timing simulation in XPLA
Professional give different results than simulation with the *.vho (or *.vo)
file?
Solution 1:
The VHO/VO files produced by XPLA Professional use worst case path
timing. This file does not distinguish signal paths through the PAL from
signal paths through the PLA. If an equation has more than 5 (4 for
XPLA2) product terms, the timing in the VHO file will show PLA timing
for all signal paths in the equation. The timing simulator in XPLA
Professional uses the actual path timing therefore if the signal path is
through a product term in the PAL, the PAL timing is used, if the signal
path is through a product term in the PLA, the PLA timing is used.
Therefore, differences can be seen in the two methods of timing
simulations. This can show up in path delays using product term clocks
as well. The XPLA Professional timing simulation simulates using circuit
details and is a more accurate representation of the actual, worst-case
device timing.
End of Record #7524 - Last Modified: 10/11/99 17:45 |
