Forum Discussion
Occasional ContributorConstraining an unclocked output?
Hi,
I am trying to achieve timing closure, but have trouble constraining outputs that is not referenced to an external clock. Do I have to define a false path for each output?
Hi,
to declare all IO as asynchronous
set_false_path -from [all_inputs]
set_false_path -to [all_outputs]
5 Replies
FvMSuper Contributor
Hi,
to declare all IO as asynchronous
set_false_path -from [all_inputs]
set_false_path -to [all_outputs]
- sstrell
If they're completely asynchronous outputs, yes, you would false path them. You can use wildcards in your target for set_false_path if there are a lot of them.
KennyT_alterasstrell is right, do you have further queries?
cjakThanks, but it is a bit unclear to me how I would define the false path:
set_false_path -from [get_pins A*] -to [get_pins B*]
...when -from and -to is the same signal/net/pin?
- KennyT_altera
- If a port (e.g., reset_in) is truly asynchronous and handled by a synchronizer, you cut the path from the port to the first synchronized flip-flop: set_false_path -from [get_ports reset_in]
