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Observer tip.can19
Observer
1,228 Views
Registered: ‎10-23-2018

Time Resolution for simulation is 1ps

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Hello,

I am using Vivado 2018.2 behavioral simulation. I have a small RTL written and trying to understand 'timescale in verilog. I understand `timescale as example `timescale 10us / 100ns where precision will be 0.1us. So I get calculation correctly while doing my behavioral simulation as per my code for reference and precision. But what is the below line I get in log file post behavioral simulation irrespective of my `timescale statement? I understand that vivado simulator uses least precision as 1ps, but in my above case it is 0.1us. What is significance of below line in any of my simulation which shows always?

Completed simulation data flow analysis
Time Resolution for simulation is 1ps

Thanks in advance,

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Xilinx Employee
Xilinx Employee
1,144 Views
Registered: ‎05-22-2018

Re: Time Resolution for simulation is 1ps

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Hi @tip.can19 ,

Yes you are correct with the first statement that  1ps is default value, but in order to overide you need to pass it throught tcl command, check below snapshot:

tsCapture.JPG

 

Thanks,

Raj

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7 Replies
Xilinx Employee
Xilinx Employee
1,201 Views
Registered: ‎05-22-2018

Re: Time Resolution for simulation is 1ps

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Observer tip.can19
Observer
1,189 Views
Registered: ‎10-23-2018

Re: Time Resolution for simulation is 1ps

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Hello @rshekhaw ,

Thank you for your kind reply. But I am not sure if it links to my query.

Though I have my simulation results correct, if I have any `timescale value in file, the behavioral simulation log shows 'Time Resolution for simulation is 1ps'. I believe the reference and precision time is correct as we defined in the 'timescale and not 1ps? Also this observation is same for `timescale 10us/10ns or any value. Can you please check my log attached? 

For reference I have printed my value of `timescale 10us/10ns of my test module which can be seen in log - Timescale of (test) is 10us/10ns.

Any idea on the significance of 'Time Resolution for simulation is 1ps' always in log?

Thanks in advance,

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Xilinx Employee
Xilinx Employee
1,161 Views
Registered: ‎05-22-2018

Re: Time Resolution for simulation is 1ps

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Hi @tip.can19 ,

Actually 1ps is default value, in order to override it you need to use "-timeprecision_vhdl" option with xelab command if you are using VHDL language, Please check below UG link page no.144:

https://www.xilinx.com/support/documentation/sw_manuals/xilinx2018_3/ug900-vivado-logic-simulation.pdf

thanks,

Raj

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Observer tip.can19
Observer
1,153 Views
Registered: ‎10-23-2018

Re: Time Resolution for simulation is 1ps

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Hello @rshekhaw ,

Thank you for your time and efforts. Actually I use verilog and not VHDL, and the link to page. 144 does not give any detail on -timeprecision_vhdl and am sure it must be typo error. Moreover I do not use non-project mode.

But I managed to research some information which I think is the answer to the question based on our useful discussion. Can you please confirm this?

1. The message 'Vivado Simulator 2018.2 <next_line> Time resolution is 1 ps' in the log is showing the default 'precision' time of the module when the simulator elaboration is setup? This is overridden by the value from the `timescale we mention in verilog module?

It is confusing because from verilog lrm, there is no mention of 'time resolution' but the formal syntax is 'timescale time_unit/time-precision.

Regards,

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Xilinx Employee
Xilinx Employee
1,145 Views
Registered: ‎05-22-2018

Re: Time Resolution for simulation is 1ps

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Hi @tip.can19 ,

Yes you are correct with the first statement that  1ps is default value, but in order to overide you need to pass it throught tcl command, check below snapshot:

tsCapture.JPG

 

Thanks,

Raj

View solution in original post

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Moderator
Moderator
1,137 Views
Registered: ‎05-31-2017

Re: Time Resolution for simulation is 1ps

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HI @tip.can19 ,

The reason why the resolution is getting overwritten to 1ps in your scenario is that in XSIM picosecond is used as a minimum resolution as mentioned at page 34 of UG900 as shown in the below snippet to crosscheck the same please change the timescale to have resolution to be fs then after running simulation, this gets replicated 

Capture.JPG

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Observer tip.can19
Observer
1,124 Views
Registered: ‎10-23-2018

Re: Time Resolution for simulation is 1ps

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okay. Thank you @shameera @rshekhaw .

Regards

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