Toggle rate, Accuracy -1, Toggle rate -1 – Altera PowerPlay Early Power Estimator User Manual
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Factors Affecting the PowerPlay Early Power
Estimator Spreadsheet Accuracy
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Many factors can affect the estimated values displayed in the PowerPlay EPE spreadsheet. In particular,
the input parameters entered concerning toggle rates, airflow, temperature, and heat sinks must be
accurate to ensure that the system is modeled correctly in the PowerPlay EPE spreadsheet.
Toggle Rate
The toggle rates specified in the PowerPlay EPE spreadsheet can have a large impact on the dynamic
power consumption displayed. To obtain an accurate estimate, you must input toggle rates that are
realistic. Determining realistic toggle rates requires knowing what kind of input the FPGA is receiving and
how often it toggles.
To get an accurate estimate if the design is not complete, isolate the separate modules in the design by
functionality and estimate the resource usage along with the toggle rates of the resources. The easiest way
to accomplish this is to leverage previous designs to estimate the toggle rates for modules with similar
functionality.
The input data in the following figure is encoded for data transmission and has a roughly 50% toggle rate.
Figure 4-1: Decoder and Encoder Block Diagram
Decoder
RAM
Filter
Modulator
Encoder
Mod Input
Data
In this case, you must estimate the following:
• Data toggle rate
• Mod input toggle rate
• Resource estimate for the Decoder module, RAM, Filter, Modulator, and Encoder
• Toggle rate for the Decoder module, RAM, Filter, Modulator, and Encoder
You can generate these estimates in many ways. If you used similar modules in the past with data inputs
of roughly the same toggle rate, you can leverage that information. If MATLAB simulations are available
for some blocks, you can obtain the toggle rate information. If the HDL is available for some of the
modules, you can simulate them.
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