when loading sdf in modelsim, warning "had null values" occurs

I saw a warning like "Out of 2774423 SDF statements, 2774423 had null values." Do it mean that the SDF annotation have some problems?

# ** Warning: (vsim-SDF-3924)E:/BMC/asic_top/post_simulation/asic_top_type.sdf: Out of 2774423 SDF statements, 2774423 had null values.


# ** Note: (vsim-3587) SDF Backannotation SuccessfullyCompleted.


Here is part of the sdf file:
(TEMPERATURE 25.00::25.00)
(TIMESCALE 1ns)
(CELL
(CELLTYPE "asic_top")
(INSTANCE)
(DELAY
(ABSOLUTE
(INTERCONNECT si_pad PIW_2/PAD (0.000::0.000))
(INTERCONNECT PX2W_0/XOUT xout_pad (-0.000::-0.000) (-0.000::-0.000))
(INTERCONNECT PIW_0/C IccPlace_2/A (0.000::0.000))
(INTERCONNECT bmc_top0/IccPostcts_3/Y bmc_top0/IccPostcts_1/A (0.000::0.000))
(INTERCONNECT bmc_top0/bmc_noio/U41/Y bmc_top0/bmc_noio/U540/A0 (0.000::0.005) (0.000::0.000))
(INTERCONNECT bmc_top0/bmc_noio/U1109/Y bmc_top0/bmc_noio/U540/A1 (-0.003::0.008) (-0.004::0.007))
(INTERCONNECT bmc_top0/bmc_noio/U96/Y bmc_top0/bmc_noio/U540/B0 (0.003::0.003) (0.003::0.003))

I don't why it says "2774423 had null values." Please help me. Thank you.

Help me! Help me!

b01010101 said:

(INTERCONNECT si_pad PIW_2/PAD (0.000:<this is the null value>:0.000))

Click to expand...

It just means in this case the nominal value is missing from the triplet of min, nomimal, max values. Just make sure there aren't any missing min or max values in the sdf.

ads-ee said:

It just means in this case the nominal value is missing from the triplet of min, nomimal, max values. Just make sure there aren't any missing min or max values in the sdf.

Click to expand...

Hi ads-ee.
Thank you very much for the reply!
So, you mean the sdf like "(INTERCONNECT si_pad PIW_2/PAD (0.000::0.000))" is OK?
And the "# ** Warning: (vsim-SDF-3924)E:/BMC/asic_top/post_simulation/asic_top_type.sdf: Out of 2774423 SDF statements, 2774423 had null values." can be ignored?
But when I run the simulation, I found that no delay are added to all the wires. And the simulation result is wrong even in 100MHz. The STA result is 500MHz.
Do you have any advice? Thank you.

You have to specify the min or Max values for annotation. I think it defaults to the nominal values.

ads-ee said:

You have to specify the min or Max values for annotation. I think it defaults to the nominal values.

Click to expand...

Thank you for your reply. Would you please explain it in detail?
I have three .sdf files: maxsdf.v, minsdf.v and typesdf.v.
I'm using typesdf.v, and in the modelsim6.2b, I use this command:
# vsim +notimingchecks -sdftyp /testbench/DUT0=E:/asic_top/bmc_core_post_simulation/type.sdf work.testbench

But I find that there are not any delay in the waveform when running. I don't know why
And the warning:
# ** Warning: (vsim-SDF-3924)E:/BMC/asic_top/post_simulation/asic_top_type.sdf: Out of 2774423 SDF statements, 2774423 had null values.

You think the warning does not matter?

b01010101 said:

I have three .sdf files: maxsdf.v, minsdf.v and typesdf.v.

Click to expand...

I'll assume you meant max.sdf, min.sdf, and type.sdf.

b01010101 said:

I'm using typesdf.v, and in the modelsim6.2b, I use this command:
# vsim +notimingchecks -sdftyp /testbench/DUT0=E:/asic_top/bmc_core_post_simulation/type.sdf work.testbench

But I find that there are not any delay in the waveform when running. I don't know why
And the warning:
# ** Warning: (vsim-SDF-3924)E:/BMC/asic_top/post_simulation/asic_top_type.sdf: Out of 2774423 SDF statements, 2774423 had null values.

You think the warning does not matter?

Click to expand...

The warning matters. It means you are annotating null values.

You are loading the typical values (-sdftyp), which are all null values, from the typical process sdf file. If you're checking timing for tapeout run -sdfmax and -sdfmin on both the max.sdf (max process corner) and min.sdf (min process corner).

Regards