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toggle rate

gops
what does a net toggle rate of .02/ns mean? Does it means that the net is going to change its value 20,000,000 times in a second?
  • Kari

     Where do you see the toggle rate specified as 0.02/ns? In the Cadence tools, toggle rate is usually specified as a percent, like 20% or 0.20. This would mean that the net is switching 20% of the time.

  • gops
    Hi Kari; Thank you for the reply. I got this info from encounter RTL Compiler low power guide.Please see the attachment.Also Kari , by saying 20% of the time; What do you mean by "time" . There is one more term called probability, defined as the probability of the activation of timing arc . If the net toggle rate is specified, then why should we give probability ? Honestly speaking , I got confused with these two terms.Can you please make these two terms clear for me?
  • Kari

     Hi Gops,

     You're right, my description of toggle rate wasn't very good. :-) I think toggle rate and toggle probability are the same thing. If you set a toggle rate of 20%, that is saying that 20% of the data nets are switching during the clock cycle.

    The probability attribute you mention from RTL-Compiler may be something different. I'm not that familiar with RTL-Compiler, but just looking at the doc for that attribute, I'm not sure you're required to set it. You may be fine just setting a toggle rate. Maybe an RC expert can weigh in here.

     - Kari

  • naderi

     This is my question too. What is  the 0.02/ns really mean?

    Although, it is mentioned that the 0.02/ns is the default value, but RC is using an equation to distribute the TR stochasticly around 0.02. This can be seen by a report from power. In such a method, it is not clear what is TR per clock. 

    Ali

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