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Background
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PET (Power Evaluation Tool) is a software tool to evaluate
the power consumption of a CMOS circuit realized with standard cells.
PET interacts with the COMPASS tools and provides accurate
evaluations with a small time overhead. Although PET can be run over
different formats (i.e. different ECAD tools), COMPASS is at the moment
the only design tool supported.
The power consumption in a CMOS cell is proportional to the output load,
to the frequency of the switching and to the short-circuit currents.
In more complex cells and sequential cells also the switching of the internal
nodes, not affecting the cell's output, dissipates power.
The model used in PET doesn't take into account transitions occurring in
internal nodes.
The expression used by PET to calculate the power dissipated by a CMOS circuit
realized with standard cells is:
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f0 (frequency) and n0 (number of transitions) are
designer's choices.
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Eint (internal energy per transition),
Ecl (energy dissipated per clock cycle) and
VDD (power supply voltage) depend on the Standard Cells Library.
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C (load capacitance) depends on the layout.
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ni and ncl (number of transitions in the nodes) depend
on the result of the simulation and on the choice of the test vectors.
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For more detail see PET references.
The figure shows the work flow of PET.
The steps to be taken when using PET are:
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Extract the netlist from the layout (i.e. file [nle])
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Run PET analyze on the netlist [nle]
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Add file [mon] to the input stimuli (generate file [csm])
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Run COMPASS sim and obtain file [trc]
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Run PET ttgen to generate file [trn]
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Run PET calpot to calculate the power dissipation
Copyright ©1996 Alberto Nannarelli,
All Rights Reserved. Last Modified: Aug 7, 1996