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AR# 31740

LogiCORE Viterbi Decoder v6.2 - When I instantiate more than one Viterbi decoder in a Virtex-5 design, implementation fails with a Pack error


When there is more than one Viterbi Decoder instantiated in a Virtex-5 design, implementation of the design fails during MAP with the following error:

"ERROR:Pack:2239 - Unable to obey design constraints (LUTNM=lutpair6amw1161)

which require the combination of the following function generator symbols

into a single LUT site:

LUT symbol "test_inst_2/blk00000003/blk00000004/blk00000290" (Output Signal

= test_inst_2/blk00000003/blk00000004/sig0000049b)

LUT symbol "test_inst_1/blk00000003/blk00000004/blk00000290" (Output Signal

= test_inst_1/blk00000003/blk00000004/sig0000049b)

LUT symbol "test_inst_2/blk00000003/blk00000004/blk0000028f" (Output Signal

= test_inst_2/blk00000003/blk00000004/sig00000496)

LUT symbol "test_inst_1/blk00000003/blk00000004/blk0000028f" (Output Signal

= test_inst_1/blk00000003/blk00000004/sig00000496)

A LUTNM constraint instance may only be applied to two function generator

symbols. Please correct the design constraints accordingly."


This is an issue with the Viterbi Decoder when the "Speed optimization" option is selected.

To work around this problem, select "Area optimization" and use area constraints for the decoders.

For a detailed list of LogiCORE Viterbi Decoder Release Notes and Known Issues, see (Xilinx Answer 29448).
AR# 31740
Date 03/27/2012
Status Archive
Type General Article