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annotating switching activity

alexsieh

Dear fellows,

 Please shine some light in how I should annotate switching activity with TCF properly.

I used "dumptcf -internal" to create a tcf file from my testbench simulation. I did not set any scope, so the tcf file annotates all of the switching activites of my DUT and of my testbench. Thats ok rite? I am assuming the RTL Compiler will ignore the switching activity recorded from my testbench and use only the numbers regarding the DUT instances. After I read the tcf file in RC and synthesize my DUT, I noticed that in the power report, some negative numbers came out.

Question1. Why does Cadence allow negative dynamic power in its report? Does it make sense?

Then, I generated tcf files using "dumptcf -internal -scope .." to each hierachical instance of my DUT. In RC, I performed multiple commands "read_tcf ...", but the numbers do not add to what the non-scoped tcf file first gave me. The power analysis came out to be much lower even though I read the tcf files of each DUT instance.

Question2. Can i have RTL Compiler make multiple tcf reads? Does it override the previous read tcf?

Hope yall can help me! Sincerely,

Alex

Parents
  • alexsieh
    Hi everybody, sorry for the taking so long.

    Thanks everybody for your help

    I have RTL Compiler v07.10-p004_1 (64bits), so I will have to update it.

    I do not have customized or special lib-files. There are all standard digital cmos.

    Unfortunately, the TCF coverage is not 100%, but I set lp_power_analysis_effort to high, so that I propagate the switching activity.

    What should be a good target number for a TCF coverage? Are power vectors suppose to be much different from the functional vectors? I believe I dont get 100% TCF coverage because my power vectors are not complete.

    I decided to generate only one tcf for the entire design, because it is easier. So I used dumptcf -internal -scope testbench.top.

    Now, I do not have to worry about the issue of reading multiple tcf files. Thank you for the explanation regarding the command. I will remember to use read_tcf -update next time.

    After reading the tcf file, the RC gives out the following summary:

    Nets/Pins asserted in TCF file : 5312
    Total Nets/Pins in TCF file    : 6514
    -------------------------------------------------------
    Asserted Primary inputs in design              : 260 (100.00%)
    Total connected primary inputs in design       : 260 (100.00%)
    -------------------------------------------------------
    Asserted sequential outputs          : 710 (100.00%)
    Total connected sequential outputs   : 710 (100.00%)
    -------------------------------------------------------
    Total nets in design                 : 20349 (100.00%)
    Nets asserted                        : 11795 (57.96%)
    Clock nets                           : 0 (0.00)
    Constant nets                        : 675 (3.32)
    Net does not have activity asserted  : 8554 (42.00%)
    -------------------------------------------------------



    Sincerely,
    Alex Sieh
Reply
  • alexsieh
    Hi everybody, sorry for the taking so long.

    Thanks everybody for your help

    I have RTL Compiler v07.10-p004_1 (64bits), so I will have to update it.

    I do not have customized or special lib-files. There are all standard digital cmos.

    Unfortunately, the TCF coverage is not 100%, but I set lp_power_analysis_effort to high, so that I propagate the switching activity.

    What should be a good target number for a TCF coverage? Are power vectors suppose to be much different from the functional vectors? I believe I dont get 100% TCF coverage because my power vectors are not complete.

    I decided to generate only one tcf for the entire design, because it is easier. So I used dumptcf -internal -scope testbench.top.

    Now, I do not have to worry about the issue of reading multiple tcf files. Thank you for the explanation regarding the command. I will remember to use read_tcf -update next time.

    After reading the tcf file, the RC gives out the following summary:

    Nets/Pins asserted in TCF file : 5312
    Total Nets/Pins in TCF file    : 6514
    -------------------------------------------------------
    Asserted Primary inputs in design              : 260 (100.00%)
    Total connected primary inputs in design       : 260 (100.00%)
    -------------------------------------------------------
    Asserted sequential outputs          : 710 (100.00%)
    Total connected sequential outputs   : 710 (100.00%)
    -------------------------------------------------------
    Total nets in design                 : 20349 (100.00%)
    Nets asserted                        : 11795 (57.96%)
    Clock nets                           : 0 (0.00)
    Constant nets                        : 675 (3.32)
    Net does not have activity asserted  : 8554 (42.00%)
    -------------------------------------------------------



    Sincerely,
    Alex Sieh
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