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AR# 14318

8.1i CPLD CoolRunner-II - "Warning:CPLD:960: or Warning:CPLD:962 - PULLUP conflicts with previous KEEPER specification"/ CoolRunner-II termination methods

Description

Keywords: 7.1i, 6.3i, 6.2i, 6.1i, 5.2i, 5.1i, 4.1i, 4.2i, 1291

Urgency: Standard

General Description:
When I implement a design, a warning message similar to one of the following occurs:

"Warning:CPLD:960: - PULLUP specified for net DATAIN conflicts with previous KEEPER specification. PULLUP is ignored."
"Warning:CPLD:962: - KEEPER specified for net DATAIN conflicts with previous PULLUP specification. PULLUP is ignored."

What do these warning messages mean? What termination methods are available in a CoolRunner-II device?

Solution

The CoolRunner-II device includes a central "global termination" circuit that can be enabled as a keeper (bus-hold) circuit or as a pull-up. This circuit can optionally be connected to any I/O pin on a pin-by-pin basis. Because there is only one global termination circuit, this means that pull-ups and keeper circuits cannot be enabled simultaneously in the same design. The warning message describes this conflict and warns that the pull-up termination request is ignored in favor of bus-hold because the hardware cannot enable both circuits. When checking for these conflicts, consult the "Unused I/O Pad Termination Mode" and "Input and Tristate Termination Mode" options in the ISE properties menu (Fitting tab/category), as well as any user-declared termination settings.

The table below shows which termination modes may be used together.

CoolRunner-II Termination Settings
CoolRunner-II Termination Settings


Notes:
1. In all these combinations, individual User I/O can have Keeper termination alone.
2. In all these combinations, individual User I/O can have Pull-up termination alone.
3. In all these combinations, individual User I/O can have either Keeper or Pull-up (not both in same design) termination.

You can use the following UCF constraint to enable pull-ups:
net datain pullup;

You can use the following UCF constraint to enable bus-hold (keeper) circuitry:
net datain keeper;

AR# 14318
Date Created 03/26/2002
Last Updated 12/19/2005
Status Active
Type General Article