1.5.9. Default Toggle Rate Assignment
You can specify a default toggle rate for primary inputs and other nodes in your design. The Power Analyzer uses the default toggle rate when no other method specifies the signal-activity data.
The Power Analyzer specifies the toggle rate in absolute terms (transitions per second), or as a fraction of the clock rate in effect for each node. The toggle rate for a clock derives from the timing settings for the clock. For example, if the Power Analyzer specifies a clock with an fMAX constraint of 100 MHz and a default relative toggle rate of 20%, nodes in this clock domain transition in 20% of the clock periods, or 20 million transitions occur per second. In some cases, the Power Analyzer cannot determine the clock domain for a node because either the Power Analyzer cannot determine a clock domain for the node, or the clock domain is ambiguous. For example, the Power Analyzer may not be able to determine a clock domain for a node if the user did not specify sufficient timing assignments. In these cases, the Power Analyzer substitutes and reports a toggle rate of zero.