check_timing Constraint

check_timing [-file <file>] [-override_defaults <checks>] [-exclude <checks>] [-verbose]

This command performs 5 types of checks by default. You can exclude or override specific defaults.

Table 1. Timing Check Types

Check Type	Description
no_clock	Report any synchronous blocks without a clock constraint.
unconstrained_internal_endpoints	Report any flipflop D pins that do not have a clock signature.
no_input_delay	Report any input ports without an input constraint.
no_output_delay	Report any output ports without an output constraint.
multiple_clock	Report clock pins that are associated with multiple clocks. This check helps find unintentional multiple clock assignments. This check also detects clock pins with dynamic clocks.

This command supports the following options:

The following example uses the no_clock and multiple_clock checks only:

check_timing -override_defaults {no_clock multiple_clock} 

The following example excludes the no_input_delay and no_output_delay checks:

check_timing -exclude {no_input_delay no_output_delay}