Architectural Limitations

The silicon architecture has a limited number of globals per device. If you create a block in a top-level design, it is recommended to minimize the number of globals when you create the block as the top-level design uses the maximum number of globals for the device, in general.

The Global Report shows the number of globals that are used for the block. To reduce the number of globals used in the block, consider clock sharing and using row globals for the block.

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

For example, to add a CLKINT after a CLK, use the following command:

define_attribute {n:CLK} syn_insert_buffer {CLKINT}