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how can I use the delay function to measure the delays between the closest rising edge of a singal_A and the following rising edge if signal_B

MFahmy

Hi, 

I am trying to use the delay function to measure the delays between a rising edge of a singal_A and the following rising edge if signal_B,

Signal_A is a periodic signal (clock) , while signal_B is a random bit stream, 

The delay function uses every rising edge from signal_A as a measurement event which is inaccurate in this case, what I am looking for is to measure the delay from the current rising edge of Signal_A to the current rising edge on signal_B and the current edge of a given signal is the latest edge, in other words, measuring the closest rising edge of signal_A to the next edge of signal_B

The triggeredDelay function works by measuring a triggering event to a rising edge after it, which also does not serve the purpose, (Tperiod - Triggered delay) can be used as a work around, but it is inaccurate as the clock signal has jitter

Thanks, 

Fahmy

virtuoso version IC23.1-64b 

sub-version  IC23.1-64b.ISR13.25

  • Hi,

    Given a case that you are trying to measure the hold time of a flip-flop with periodic clock and random data.

    My previous experience on this is to combine triggeredDelay and rshift. Basically, the idea is to right-shift clock signal with delta X being equal to period, then using triggeredDelay to measure setup time of data compared to shifted-clock. Last step is to subtract your 'calculated setup' from Tperiod to get 'real hold'.

    Ex: (2*VAR("UI")) - ymax(triggeredDelay(clip(VT(din), tc_start, tc_stop) rshift(clk_diff (2*VAR("UI"))) (VAR("vddavs") / 2) "either" 0 "falling"))

    However, a more compatible function has been defined by Cadence:

    support.cadence.com/.../ArticleAttachmentPortal

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