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AR# 9982

4.2i ABEL2EDIF - "Internal Error 18897: pop_cell not connected."

Description

Keywords: ABEL, BLIF2NET, ISE, pop_cell, 18897, ABEL2EDIF

Urgency: Standard

General Description:
As I compile an ABEL design, the following error message is reported:

"Internal Error 18897: pop_cell not connected."

Solution

A problem with the ABEL-BLIF flow in ISE triggers this error for certain designs that have combinatorial feedback. If the feedback is in a combinatorial loop, you can work around the issue by:

1. Using the ABEL-XST flow, or;

2. Breaking the combinatorial loop by synchronizing one or more of the signals in the loop. (We recommend that combinatorial loops be avoided as a general design practice.)

If the feedback is not from a combinatorial loop, it may be possible to work around it by editing the ABEL file to remove the feedback. For example:

a=c&d&e;
b=!a;

could be changed to:

a=c&d&e;
b=!(c&d&e);

Use of the ABEL-XST flow should work in any case; this will be the preferred flow going forward.
AR# 9982
Date Created 08/31/2007
Last Updated 08/12/2003
Status Archive
Type ??????