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# problem with vcd file

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#### ne.me.sis

##### Newbie level 6
vcd strip path

Hello. Would like to know the common ways(or eda tools) that are used to estimate power for IC, both digital and analog. Can it be done for gated clock design? How is the accuracy? Please share your experiences and thoughts. Thanks.

#### Garbielhijo

##### Newbie level 5
simulation vcd dumpvars

I use a littler bit of Astro Rail for power analysis, is good for this task but I used it just for digital analysis. All the analog section was implemented as a hard macro with a model for the power and switching.

#### stevepre

##### Member level 4
vcd file error

Use gatelevel simulation on post-P&R netlist.
The result is very close to lab data.

#### ne.me.sis

##### Newbie level 6
obtain+vcd+file+from+sdf

Hello Garbielhijo, can you elaborate a little bit more on power analysis with astro rail. What are the inputs that it take in and what are the outputs?

Hello stevepre, how do you extract the power data from post P&R simulation? I don't get you.

Actually, I never do power estimation for my chip before, but right now I am looking for a method so that I can have better control of the power comsumption. Therefore, please explain more when you chip in your comments/ideas. Thanks.

#### stevepre

##### Member level 4
saif file astro

Using any backend flow is going to take a long long time. Not practical.

Using any RTL power estimation is way off reality.

Using gatelevel simulation (after P&R gate, so the clock tree is there).
Basically, the flow is: you prepare the gatelevel netlist, get SDF from backend people as well as parasitic information (the cap and resistor) file from backend people as well.

Option 1: Run gatelevel simulation with SDF, dump VCD ==> well...the size of VCD easily goes beyond 4G, so....you have to control your simulation time and positiion very well.

Option 2: similiar to option 1, but dump FSDB file. Synopsys primepower can read in streaming FSDB file and calculate the power.

Option 3: run gatelevel simulation, but link the PLI to dump SAIF file instead of VCD or FSDB.

Calculate the power from either one of the above 3 options with primepower.
but with option 3, you won't get power-vs-time chart. But you get one number over your simulation period. But it's as accurate as others (over that period of time)

#### pandit_vlsi

##### Member level 3
astro read saif error

hi.
power can be estimated right from rtl to post layout.as size of the chips is decreasing...so powr estimation is beginning right from rtl.
there is prime theatretool to get power at rtl level,prime power tool at netlist,astrorail&blast rail ,redhawk at post layout level.
i used redhawk at post layout for both static&dynamic ir drop analysis.
...
pandit

#### jcchan

##### Member level 1
how is the input file for a vcd calculations?

power can be estimated from the cell toggle so designer know the total cell toggle rate in normal function to estimate the all transaction current in clock rising or falling then to decide the power ring width.

#### jzhangsun

##### Newbie level 6
how to do vcd power estimation

hi pandit_vlsi

i am interesting in power analysis tool at RTL level,would you like tell me the typical tool that
is available now.

#### stevepre

##### Member level 4
primepower fsdb

sequence design, powertheater

#### ne.me.sis

##### Newbie level 6
size+vcd+file+synopsys

Anyone run power estimation with vcd file before? I received warnings that nets are not covered by VCD file and an error,"Error: (read_vcd) Strip path can not be matched in the VCD file.

What I did are:
1) In testbech,

initial
begin
$dumpfile("top.vcd");$dumpvar("0,top");
end

2) Run sim and obtain top.vcd

3) Read in gate netlist, spef file and vcd file in prime power.

Anything wrong with my steps? How should I verify those nets are in the vcd file?

Another question is how to clip the time so that we can get an accurate vcd for power calculation? Doing it manually after getting the vcd file or there is other ways to do so?

I noticed that the vcd file can easily become very large. How to handle and manage the vcd file? I read an article in solvenet, where we can split the vcd file. Anyone has tried before?

Thanks.

#### manu_leo

##### Member level 1
vcd dumpvars

if ur using powertheater use -mixed option rather than full simulation one.
Basically the tool searches for all the nets toggle information from vcd file, if that is not there gives out wn error. If u use -mixed option, it will do probablistic estimation.

#### tinu90

##### Newbie level 3
is not covered by vcd file

ne.me.sis said:
Anyone run power estimation with vcd file before? I received warnings that nets are not covered by VCD file and an error,"Error: (read_vcd) Strip path can not be matched in the VCD file.

What I did are:
1) In testbech,

initial
begin
$dumpfile("top.vcd");$dumpvar("0,top");
end

2) Run sim and obtain top.vcd

3) Read in gate netlist, spef file and vcd file in prime power.

Anything wrong with my steps? How should I verify those nets are in the vcd file?

Another question is how to clip the time so that we can get an accurate vcd for power calculation? Doing it manually after getting the vcd file or there is other ways to do so?

I noticed that the vcd file can easily become very large. How to handle and manage the vcd file? I read an article in solvenet, where we can split the vcd file. Anyone has tried before?

Thanks.

1. Try dumping VCDs at partition level and not Full Chip
2. initial
begin
$dumpfile("top.vcd");$dumpvar("0,top"); <----Not sure if this is effective. Try "vcd add -r hierarchy/*"
end
3. I assume you are using MODELSIM for your simulations
try this
vcd file dummy_vcd.vcd
vcd add -r hierarchy/*
4.
Anything wrong with my steps? How should I verify those nets are in the vcd file?
When you run the PP tool, look for VCD annotaion. This is a good indicator as to how the annotation occurs

#### ganeshgarg

##### Newbie level 1
vcd vs. fsdb

Instead of using only read_vcd to read in the vcd file, use the following:

read_vcd -strip_path <testbench module name>/<dut instance name> <vcd filename>

#### paulki

##### Full Member level 2
scansion vcd hierarchy

Hi all,
For Power calculation there are couple of tools available and all these required different types of waveform dumps (boundary VCD, SAIF, etc)
PowerCompiler is good tool to calculate Power and you need to run the GLS (Typically Zero_Delay) performance test to dump the SAIF. And this SAIF is the input to the PowerCompiler.

Thanks,
-Paul

#### kapil_vlsi1

##### Member level 2
primepower fsdb power calculation

Please send Astro Rail Workshop Guide if anybody has?

Thanx

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