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DC_SHELL, synopsys

perseo perseo is offline
Junior Member
Join Date: Oct 2007
Posts: 3
Hi everybody,

Iīm working with Synopsys and my problem is my experiments donīt fit to theory. Iīm measuring power and I donīt know what is failing if anything is really failing.

Well, power is divided in two components
1) Static
2) Dynamic. And dynamic power is also divided in two components:
2.1) Net switching power, due to charge and discharge of output capacitance
2.2) Cell internal power

Well, according to synopsys' (and I think everybody's) theory, net switching is more or less 90% of dynamic power, while cell internal power could reach a 30% peak in circuits with few transitions.

However, my results are

Global Operating Voltage = 2.5
Power-specific unit information :
Voltage Units = 1V
Capacitance Units = 1.000000ff
Time Units = 1ps
Dynamic Power Units = 1mW (derived from V,C,T units)
Leakage Power Units = 1mW

Cell Internal Power = 644.8631 nW (66%)
Net Switching Power = 329.3489 nW (34%)
Total Dynamic Power = 974.2120 nW (100%)

Cell Leakage Power = 33.4626 nW

Iīm using two scripts for achieving power results.


power_preserve_rtl_hier_names = true
analyze -format vhdl -lib WORK "./prueba.vhd"
elaborate prueba -arch "beh1" -lib WORK -update
rtl2saif -output "prueba.RT.saif" -design "prueba"


sh "vcd2saif -i prueba.vcd -o prueba.saif -rtl prueba.RT.saif -strip prueba"
elaborate prueba -arch "beh1" -lib WORK -update
read_saif -input prueba.saif -instance top

Well, the .vcd file (stimulus file) is obtained by simulating values with modelsim.

One thing Iīve tried is varying bit by bit the inputs in the macro of modelsim, but I only get an increase of 15 nW in net switching power, what is very little.

I donīt know what is happening. Any idea ??

Thank you a lot
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