Hello,
for my clock tree synthesis, I use the ccopt flow, and I source the following commands:
setCTSMode -engine ccopt
create_ccopt_clock_tree_spec -file ccopt.spec
The .spec file should be based on my .sdc. However, in the generated .spec file I can read something like the following:
# Clock tree offset inferred from set_clock_latency -source assertions:
set_ccopt_property source_latency -delay_corner corner_max_125c -late -rise -clock_tree CK_4 -0.273
set_ccopt_property source_latency -delay_corner corner_max_125c -late -fall -clock_tree CK_4 -0.276
set_ccopt_property source_latency -delay_corner corner_min_m55c -early -rise -clock_tree CK_4 -0.125
set_ccopt_property source_latency -delay_corner corner_min_m55c -early -fall -clock_tree CK_4 -0.126
However I don't have any set_clock_latency command in my .sdc!!!
Where do these numbers come from? And why they're negative?
I hope you can help me understand. Thanks!!!