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AR# 24864

LogiCORE PCI v4.2 and PCI-X v6.2 - "ERROR:Place:864 - Incompatible IOB's are locked to the same bank 3; List of locked IOB's: RCLK_N and RCLK_P"

Description

Keywords: MAP, map, DIFF_TERM, VCCO, 2.5

When implementing PCI v4.2 cores or PCI-X v6.2 cores in PCI mode, you might receive errors in MAP as a result of the placement of RCLK_N and RCLK_P. The following error can occur:

"ERROR:Place:864 - Incompatible IOB's are locked to the same bank 3
Conflicting IO Standards are:
IO Standard 1: Name = LVDS_25, VREF = NR, VCCO = 2.50, TERM = NONE
List of locked IOB's:
RCLK_N
RCLK_P

IO Standard 2: Name = PCI33_3, VREF = NR, VCCO = 3.30, TERM = NONE
List of locked IOB's:
PCLK
IDSEL
GNT_N
RST_N

These IO Standards are incompatible due to VCCO mismatch."

Solution

This occurs if the RCLK_P and RCLK_N inputs use the DIFF_TERM=True constraint and are placed in the same bank as other PCI-related pins. The UCF syntax would appear as:

NET "RCLK_P" LOC = "H19" IOSTANDARD = LVDS_25 | DIFF_TERM = TRUE;
NET "RCLK_N" LOC = "H20" IOSTANDARD = LVDS_25 | DIFF_TERM = TRUE;

To fix this problem, either remove DIFF_TERM=True and use external termination, or move the RCLK_N and RCLK_P inputs to a bank with Vcco set to 2.5 volts.

For more information on the DIFF_TERM = True constraint, please refer to the Virtex-5 User Guide found at:

http://www.xilinx.com/support/documentation/virtex-5.htm#19297

Revision History
07/14/2008 - Update link to Virtex-5 UG
AR# 24864
Date Created 09/04/2007
Last Updated 07/15/2008
Status Active
Type General Article