1.3.5 Architecture Limitations - Managing Blocks and Global

Architecturally, the silicon has 8 or 16 globals per device, depending on the device size. If you create a block used in the top level design that uses the maximum number of globals close to the device, then it is a good practice to minimize the number of globals when you create the block.

Examine the global report to see the number of globals that is used for the block. To reduce the number of globals used in the block, you may consider clock sharing and the use of row global for the block.

To add an internal global on a port, use either the Synplify Constraints Editor (SCOPE) or an SDC file.

To add a CLKINT after a CLK port, the command is: define_attribute {n:CLK} syn_insert_buffer {CLKINT}.