AR# 10599

FISE 3.1 - ABEL-XST flow may create incorrect logic for bi-directional pins.

Description

Keywords: ABEL, XST, tri-state, 3-state, bi-directional, pin feedback

Urgency: Standard

General Description:
In cases where the input of a bi-directional port drives another output pin, the
ABEL-XST flow can create incorrect logic.

EXAMPLE:
IO_A, IN_A, OUT_ENABLE, OUT_B pin;
Equations
IO_A = IN_A;
IO_A.oe = OUT_ENABLE;
OUT_B = IO_A.pin;

Solution

If you have a pin configuration in your design similar to the description above, you
should use the ABEL-BLIF flow for the Foundation ISE 3.x release.

The above signal configuration will compile and implement correctly using the
ABEL-BLIF flow.

This ABEL-XST problem will be corrected in the next major software release.
AR# 10599
Date 08/15/2002
Status Archive
Type General Article