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Simulators >> Logic Simulators >> HOW TO INTERPRET VCD FILE
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Message started by vinncog on Feb 10^th, 2006, 1:16am

Title: HOW TO INTERPRET VCD FILE
Post by vinncog on Feb 10^th, 2006, 1:16am

Can somebody pls explain to me how to interpret a vcd file?
i have looked into the modelsim documentation, and it only mentions rules for few combinations. those items with question mark are those that i dont know (though im not sure also if those that i put some answers on are correct, so feel free to correct me).
ex.
input value output value input strength ouput strength output value (in vcd) output strength (in vcd)
0 0 7(strong) 7(strong) ? ?
0 0 7(strong) 6(strong) 0 input strenght
0 0 7(strong) 5(strong) 0 input strength
0 0 strong weak D input strength

0 1 7(strong) 7(strong) ? ?
0 1 7(strong) 6(strong) ? ?
0 1 7(strong) 5(strong) ? ?
0 1 strong weak D input strength

N 0 ? 7(strong) ? ?
N 0 ? 6(strong) ? ?
N 0 ? 5(strong) ? ?
N 0 ? weak ? ?

N 1 ? 7(strong) ? ?
N 1 ? 6(strong) ? ?
N 1 ? 5(strong) ? ?
N 1 ? weak ? ?

thank you very much for your help....

Title: Re: HOW TO INTERPRET VCD FILE
Post by jbdavid on Jan 22^nd, 2007, 9:05pm

I spent a lot of time looking at VCD and EVCD a couple of years ago, now I all I can say is to look at 1364-2001, I believe VCD is covered in section 18!

Title: Re: HOW TO INTERPRET VCD FILE
Post by jbdavid on Jan 22^nd, 2007, 9:09pm

VCD only reports state as
0 1 X or Z
NO STRENGTH info, no direction info,
if you want that, you need EVCD

Again, the details are in IEEE 1364-2001 section 18