Routing delay in timing report after PnR for ASIC

[sun_ray]

Where is routing delay reported in case of ASIC PnR, . After PnR there is report for cell delay as I find in the timing report. Where can I find the routing delay?

Regards

 

[rca]

In PnR and STA tools, you could add arguments to report also the net delay in your report timing command.

 

[sun_ray]

In PnR and STA tools, you could add arguments to report also the net delay in your report timing command.

Is it that then the timing report will have a separate table containing all the nets in a path and stating the delay for each net in that particular path similar to the way the timing report contain a table stating the delay for all the cells in a particular path?

How do engineers utilize this routing delay?

I send you a personal message to reply to one thread. Please reply to that thread.
Regards

 

[gliss]

When you add net information to timing reports (like -nets for PrimeTime's report_timing command for example), the net delay information is added to the same table as the cell delay information.
Engineers can use this information to find out if their path delays are wire dominated or cell dominated.

 

[sun_ray]

Do you want to mean that in the same table tool will report the timing for cells along with nets for a particular path when timing is reported with the -nets option?

 

[gliss]

Yes, incremental delays from the nets and the cells are explained in the timing report for the path with the -nets option for PrimeTime's report_timing.

 

[sun_ray]

Yes, incremental delays from the nets and the cells are explained in the timing report for the path with the -nets option for PrimeTime's report_timing.

Is it that for a particular path in the timing report, the same table will include both the cell and net delay for that path?

 

[sam536]

report_timing -nets -inp -cap options in PT will report the routed net delay information on the routed design. Waht is mean by table here. You need to know the dealy of the net . Isnt it?. you can even use report_delay_calculation -from <> -to <> to find the causes/factors for the delay calculations .

Regards, Sam

 

[sun_ray]

By table I mean a table that will contain an entire timing path (e.g. a complete reg-reg path). By some PnR tools, after PnR the timing report reports the timing of an entire path in a table.

I have another question :

Is it that no PnR tool can report the net delay exactly in the way the STA tool report the net delays?

 

[sam536]

I hope first question is answered. I interpret tables as delay table in .lib. Ok. Good. Timing report with above commands generate your required tables.

second question. Yes. The net delay or cell delay variation is expected from STA to PNR tools. Because the delay engines are differnt in differnt tools. these delays calculation tools are based on the algorithms , which EDA vendor depends on.

How to over come this variation ?.

We use margins in STA and PNR tools. Compared to Signoff STA valuee, we use 100-200ps margin in P&R tools to over come these type of issues depends on the technology nodes. we do have EDA tool differential margins also while considering for optimization.

Regards,
Sam

 

[rca]

the report timing between pnr & sta should match at the 10*picosecond without SI. To aligne the net delay, you need to adjust the net delay calculation in PnR versus the STA signoff.
The tool ostrich for example compare the SPEF from PnR versus the spef from parasitic sign off extraction, and generate the factor needed to align.
After this step, the majority of the path should met.

When the SI mode is enable, the engines are different between all tools, but the difference should be inside the margin and not really relevant.

 

[sun_ray]

I hope first question is answered. I interpret tables as delay table in .lib. Ok. Good. Timing report with above commands generate your required tables.

SAM536

No, table is not the delay table in .lib. Let me explain you what I MEAN BY TABLE. Some tool report the timing by tabulating each path. Here in a table, it will describe all the cells that are present in that particular timing path for which the table stands. The table will contain the delays also for all the cells that are present in that particular timing path for which the table stands. Some tools just enclose the timing path in a table and some tools do not enclose in a table after you use the report timing command. Is it clear now? Once the timing report is opened there the paths may be in a table or may not be in tabular form also, depending on the tool.

Regards