Timing Constraint Editor > Constraints > Clock {standard to present this info TBD}
Use this command to enter the clock constraint settings. The command displays a typical clock waveform populated with clock information items currently available. You can enter or modify this information, then save the final settings as long as the constraint information is consistent. The tool displays errors and warnings in case information is missing or incorrect.
You can edit the following fields:
Enables you to choose a pin from your design to use as the clock source.
The drop-down list is populated with all obvious clocks. You can also select the Browse button to access all potential clocks. The Browse button displays a Clock Source Selector dialog box.
Instant zero used as a common starting time to all clock constraints.
When you edit the period, the tool automatically updates the frequency setting accordingly.
The period must be a positive real number. Accuracy is up to 3 decimal places.
When you edit the frequency, the tool automatically updates the period setting accordingly.
The frequency must be a positive real number. Accuracy is up to 3 decimal places.
Enables you to switch between rise and fall edge and updates the clock waveform accordingly.
If the current setting of starting edge is rising, you can change the starting edge from rising to falling.
If the current setting of starting edge is falling, you can change the starting edge from falling to rising.
{Link to TBD how part}
This number specifies the percentage of the overall period that the edge is high.
The duty cycle must be a positive real number. Accuracy is up to 4 decimal places. Default value is 50%.
The offset must be a positive real number. Accuracy is up to 2 decimal places.
{Do we need this?} If the first edge is rising, the offset must be less than the period * ( 1 – ( duty-cycle / 100 ) ). If the first edge is falling, the offset must be less than the period * ( duty-cycle / 100 ).
Enables you to save a single line text to describe the clock constraint purpose.
