Description

Keyword: Spartan-XL, Synplicity, clock, infer, global, buffer 

General Description: 

Synplify limits global buffer insertion to four. However, in some architecture (such as Spartan-XL), a design can use up to eight BUFGLS. How do I change BUFG limit from 4 to 8 for these architectures?

解决方案

Set the following attribute in the .sdc file to increase the limit of BUFG insertion in Synplify: 

define_global_attribute xc_global buffers (8)