The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design Languages >> Verilog-AMS >> transition function in Verilog-A
https://designers-guide.org/forum/YaBB.pl?num=1396627087

Message started by prcken on Apr 4^th, 2014, 8:58am

Title: transition function in Verilog-A
Post by prcken on Apr 4^th, 2014, 8:58am

Hi All,
Due to absdelay function can't support AC simulation, so I use transition function instead. I just want to delay the signal from the previous block, not redefining the rise and fall time. But I found after changing to transition function, the results from transient simulation seem not correct. Please advise!
Thanks!

//OptPower(OutOptPower) <+ absdelay((OptPower(InOptPower_top)+OptPower(InOptPower_bot)) * Topt, prop_delay);
//OptPhase(Phase_probe) <+ absdelay(phase_diff,[0]);
OptPower(OutOptPower) <+ transition((OptPower(InOptPower_top)+OptPower(InOptPower_bot)) * Topt, prop_delay);
OptPhase(Phase_probe) <+ transition(phase_diff,[0]);

If neither rise nor fall time are specified, the rise and fall time are taken to be one unit of time (as defined by the timescale complier directive) and no attempt is made to control the time step to follow the trailing corner on the transition.
I am wondering is there any other function can support both tran and ac simulation?

Title: Re: transition function in Verilog-A
Post by Ken Kundert on Apr 5^th, 2014, 1:57am

The argument to a transition function must be piecewise constant, so it cannot be used to delay an AC signal.

The only way to do what you want would be to instantiate a built in primitive that implements delay. If you are using spectre, you can implement a delay component.

-Ken

Title: Re: transition function in Verilog-A
Post by prcken on Apr 5^th, 2014, 2:14pm

Thank you so much, Ken!