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AR# 25159

9.1i - PAR - "ERROR:Place:864 - Incompatible IOB's are locked to the same bank" on LVDS_25 inputs on a 3.3V bank

Description

Using ISE 9.1i, I receive the following error that I did not receive previously in ISE 8.2i.

ERROR:Place:864 - Incompatible IOB's are locked to the same bank 3

Conflicting IO Standards are:

IO Standard 1: Name = LVCMOS33, VREF = NR, VCCO = 3.30, TERM = NONE

List of locked IOB's:

fn_tst

core_rst_pin

IO Standard 2: Name = LVDS_25, VREF = NR, VCCO = 2.50, TERM = NONE

List of locked IOB's:

clkn_400

clkp_400

Is this a valid error message, and what is causing it?

Solution

This is a valid error. Although the LVDS buffers are powered by VCCAUX, the differential terminations are powered by VCCO and are required to be placed in a 2.5V bank.

This check was added in ISE 9.1i to ensure that the correct differential termination was seen in hardware. Due to the software defect that is scheduled to be fixed in a future ISE release, the TERM = NONE listed in the error message does not guarantee that differential termination was not used.

For more information about on-chip input differential termination, please reference (Xilinx Answer 17244).

AR# 25159
Date Created 10/22/2008
Last Updated 12/15/2012
Status Active
Type General Article