Lattice Diamond: How to set the behavior of unused pins in an FPGA design?
Solution:
1) In RTL code, assign the following attributes to the unused input:
/* synthesis syn_force_pads=1 syn_noprune = 1 */
2) For Synplify Pro flow, under Strategy1 make the following setting:
MAP Design--> Command line options = -u
This ensures that the Mapper does not remove the unused I/Os.
3) In Spreadsheet View, you can modify the setting as needed.
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