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AR# 19715

Synplify 7.3 - MAP does not pack my I/O FFs into IOBs


General Description:

When I run my HDL code through Synplify for synthesis and select 'Pack I/O Registers/Latches into IOBs' in MAP, I see in the MAP Report that 8 Registers have been packed into IOBs. When I use XST for synthesis and set the same option, I get 40 registers packed into IOBS. Why does MAP not pack as many FFs into IOBS when the netlist comes from Synplify?


Synplify sets a property (property IOB (string "FALSE")) to I/O FFs by default. This overrides the value set in MAP to pack IO Registers into IOBs.

To set (property IOB (string "TRUE")) in the netlist, set the syn_useioff attribute in your HDL code. Refer to the Synplify User Guide for more information on how to use this attribute.
AR# 19715
Date Created 09/03/2007
Last Updated 03/14/2012
Status Archive
Type General Article