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AR# 21630

7.1i XST - A design that fits in 6.3i does not fit in 7.1i when using finite state machines with CPLD devices

Description

Keywords: Fit, Design, state, machine, does, not, CPLD, xst

Urgency: Standard

General Description:
A design that fits in 6.3i does not fit in 7.1i when using finite state machines with CPLD devices.

Solution

In XST 7.1i, the synthesis algorithm has changed.

In XST 7.1i two Finite State Machines are inferred instead of one by default for better timing. To get the same behavior as with the prevision version, you can set the following switches:

-fsm_extract NO
-fsm_encoding compact

To see how to set these switches, please refer to the Project Navigator help if in GUI mode or the XST User Guide if in command line mode.
AR# 21630
Date Created 06/22/2005
Last Updated 01/08/2009
Status Archive
Type General Article