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AR# 668

FITNET/FITEQN: packing more pterms into an FFB macrocell

解决方案




PROGRAM: FITEQN, FITNET

VERSION: 5.0, 5.1

PLATFORM: All

SHORT DESCRIPTION:

A way to pack more pterms into a Fast Function Block macrocell


LONG DESCRIPTION:

PROBLEM:

Currently the fitter used in 5.0 and 5.1 allows a default of 4 product terms
maximum in an FFB output. This causes the fitter to break up large equations
into multiple macrocells.

This results in two problems:

1) It slows the design down.

2) It can waste resources. This happens if the equation is later DeMorganed
to use fewer than 4 pterms. In this case, the software could have fit the
equation into a single macrocell instead of splitting it.

SOLUTION:

Copy the file XACT\DATA\XEPLD.CFG into the project directory. Edit the last
line:

alias ffb_pterm_limit 36

so that it is surrounded by parentheses:

(alias ffb_pterm_limit 36)

This will change the maximum to 36 pterms.

Note: The 5.2 software will automatically default to 36.


AR# 668
创建日期 08/31/2007
Last Updated 11/05/1996
状态 Archive
Type ??????