Answers Database

M1.4 CPLD Fitter: Combinatorial logic duplicated with multilevel logic optimization


Record #3730

Product Family:  Software

Product Line:  CPLD Implementation

Problem Title:
M1.4 CPLD Fitter: Combinatorial logic duplicated with multilevel logic
optimization



Problem Description:
Keywords: multi, level, logic, optimization, hitop, cominatorial. duplication

Urgency: Standard

General Description:

The CPLD Fitter may duplicate combinatorial logic (2 inpus OR gates) feeding con
trol
signals (CLK, SR, OE, CE) during multi-level optimization increasing
the macrocell count.



Solution 1:

IF you run into this situation, you can resolve the issue in
either of two ways.

1. Turn off multi-level logic optimization from the Advanced
optimization tab in the Design Manager, XC9500 template. This
may cause other optimization/fitting problems.

2. Use the KEEP attribute on the 2 inpit OR gates feeding the
control logic. This is a better solution.





Solution 2:

A fix is available for this problem in the latest CPLD Tools
update available on the Xilinx Download Area:

ftp://ftp.xilinx.com/pub/swhelp/M1.4_alliance/cpld_sol9_m14.tar.Z
ftp://ftp.xilinx.com/pub/swhelp/M1.4_alliance/cpld_sun9_m14.tar.Z
ftp://ftp.xilinx.com/pub/swhelp/M1.4_alliance/cpld_hp9_m14.tar.Z
ftp://ftp.xilinx.com/pub/swhelp/M1.4_alliance/cpld_nt9_m14.zip

These update files also include the changes from previous cpld updates.

All zip files are created using WinZip. To obtain this utility,
access WinZip's web site at http://www.winzip.com




End of Record #3730