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452 Views
Registered: ‎10-30-2019

set_clock_uncertainty command seen in critical message

Hi,

I am getting a critical message as below

[Common 17-1548] Command Failed: Error: unknown error occurred in line 6 (line 6 contains set_clock_uncertainty as shown below )

for the following command of set_clock_uncertainity

 

create_clock -name v_phy_apb4_clk -period 2.22

create_clock - name phy_apb4_clk -period 2.22

set_clock_uncertainty -setup 0.222 [get clocks v_phy_apb4_clk phy_apb4_clk]

I am not able to get why this issue is coming. 

The Vivado version is 2018.2

Regards,

Saket

6 Replies
Moderator
Moderator
409 Views
Registered: ‎02-09-2017

Re: set_clock_uncertainty command seen in critical message

Hi @saket_cortech,

Does the Warning mentions anything further about why this command failed?

In most cases, when I see such commands failing, its because the tool cannot find the clock you are trying to apply the constraint to.

One issue I see in your command is that you are adding the name of both clocks in one single command  (v_phy_apb4_clk and phy_apb4_clk).

What is it that you are trying to do? Are you trying to apply a setup uncertainty to both clocks individually? Or are you trying to apply uncertainty between the clock domains?

In the first case, you need to add two constraints, one for each clock, as below:

set_clock_uncertainty -setup 0.222 [get clocks v_phy_apb4_clk]
set_clock_uncertainty -setup 0.222 [get clocks phy_apb4_clk]

In the second case (uncertainty between the two clock domains) you need to use the following command:

set_clock_uncertainty 0.222 -from [get_clocks v_phy_apb4_clk] -to [get_clocks phy_apb4_clk] 

Thanks,

 

Andre Guerrero

Product Applications Engineer

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408 Views
Registered: ‎10-30-2019

Re: set_clock_uncertainty command seen in critical message

Hi @anunesgu ,

The tool is not giving any specific reason for the failure apart from the message it is throwing which I have mentioned earlier.

Also applying uncertainty separately also does not work.

set_clock_uncertainty -setup 0.222 [get clocks v_phy_apb4_clk]
set_clock_uncertainty -setup 0.222 [get clocks phy_apb4_clk]

Regards,

Saket

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Moderator
Moderator
401 Views
Registered: ‎02-09-2017

Re: set_clock_uncertainty command seen in critical message

Hi @saket_cortech,

In which stage of the design are you? Pre-synthesis, after Synthesis, after Implementation?

Normally, these constraints will only work after synthesis, because before that the tool doesn't even know that those clocks exist.

By the way, could you please run the command below and see if the tool returns a clock object or a Null/Error:

get clocks v_phy_apb4_clk
get clocks phy_apb4_clk

 Thanks,

Andre Guerrero

Product Applications Engineer

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Historian
Historian
372 Views
Registered: ‎01-23-2009

Re: set_clock_uncertainty command seen in critical message

First, I assume everywhere you write "get clocks" you really mean "get_clocks" (with an underscore).

But the root of the real problem is that "get_clocks" takes a single option - either the name of one clock or a list of clocks. You gave it two options, each a name of a clock. So the command should have been

set_clock_uncertainty -setup 0.222 [get_clocks {v_phy_apb4_clk phy_apb4_clk}]

the {} create a list of clock names.

Avrum

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294 Views
Registered: ‎10-30-2019

Re: set_clock_uncertainty command seen in critical message

Hi @anunesgu,

This command is being run post-synthesis.

I am not getting the error also the same clock is being used for set_input_delay and for that error is not coming which also confirms that the clock has been created.

I have attached the snapshot of the constraints - lines 17-21 contain set_input_delay constraint which is using the same clock.

Constraints.PNG

Regards,

Saket

 

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293 Views
Registered: ‎10-30-2019

Re: set_clock_uncertainty command seen in critical message

Hi @avrumw,

You are correct I am using get_clocks command.

I tried to use {} brackets to pass multiple clocks but it didn't work out.

Regards,

Saket 

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