Altera PowerPlay Early Power Estimator User Manual

Page 29

Chapter 3: Using Cyclone III PowerPlay Early Power Estimator

3–17

PowerPlay Early Power Estimator Inputs

PowerPlay Early Power Estimator User Guide for Cyclone III FPGAs

Table 3–8

describes the parameters in the Clock section of the PowerPlay Early Power

Estimator.

Figure 3–11

shows the Clocks section of the PowerPlay Early Power Estimator and

the estimated power consumed by clocks.

Table 3–8. Clock Section Information

Parameter

Description

Domain

Enter a name for the clock network in this column. This is an optional value.

Clock Freq (MHz)

Enter the frequency of the clock domain. This value is limited by the maximum frequency
specification for the device family.

Total Fanout

Enter the total number of flip-flops and RAM, DSP, and I/O blocks fed by this clock. The number of
resources driven by every global clock signal is reported in the Fan-out column of the Quartus II
Compilation Report. In the Compilation Report, select Fitter and click Resource Section. Select
Global & Other Fast Signals and click Fan-out.

Global Enable %

Enter the average % of time that the entire clock tree is enabled. Each global clock buffer has an
enable signal that can be used to dynamically shut down the entire clock tree.

Local Enable %

Enter the average % of time that clock enable is high for destination flip-flops.

Local clock enables for flip-flops in LEs are promoted to LAB-wide signals. When a given flip-flop is
disabled, the LAB-wide clock is also disabled, cutting clock power in addition to power for



down-stream logic. This sheet models only the impact on clock tree power.

Total Power

This is the total power dissipation due to clock distribution (in W). This value is calculated
automatically.

User Comments

Enter any comments. This is an optional entry.

Figure 3–11. Clocks Section in the PowerPlay Early Power Estimator