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AR# 21699

7.1i EDK SP2 - PLB/OPB_EMC 2.00.a 3-state registers cannot be packed into IOBs


General Description:

PLB/OPB_EMC 2.00.a 3-state registers cannot be packed into IOBs.

"The reason that the 3-state registers cannot be pushed into the IOB is because the registers are optimized down to one register and all of the 3-state lines are driven from the one slice register. A save attribute will probably keep XST from doing this optimization. "

So, add the following attributes in "plb_emc.vhd" to successfully pack all (input/output/3-state) registers into IOBs.

attribute equivalent_register_removal: string;

attribute equivalent_register_removal of Mem_DQ_T : signal is "no";

attribute iob: string;

attribute iob of Mem_DQ_T : signal is "true";

Changes were made to the plb_emc_v2_00_a, opb_emc_v2_00_a, emc_common_v2_00_a and libraries.


This problem has been fixed in the latest 7.1i EDK Service Pack available at:

The first service pack containing the fix is 7.1i EDK Service Pack 2.

AR# 21699
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article