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how to specify internal net as scanmode signal

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animotion

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All,

I need to define a certain internal signal in my synthesized netlist to be the scanmode signal for DFT.

How is this possible in DFT compiler? (Do I use the set_sft_signal command..?)

In the netlist, this internal signal is the output of combinational logic. The input into
this logic is dft_tst<2:0>. i.e. the scanmode signal is one of the 8 dft_tst testmode settings.

-animotion
 

Yes you can, only if the Tester (and DFTAdvisor) can fully access (via Primary Inputs) & control the combinatorial logic which outputs the internal 'scanmode' signal.
 

roli,

The tester will have access to (and control of) the dft_tst<2:0> which is the input to the combinatorial logic that controls the internal "scanmode" signal

Would you have the DFT Compiler command that ensures that the internal "scanmode" signal is recognised as such by DFT compiler?

Thanks
animotion
 

you may try the option -hookup_pin of set_dft_signal.
 

animotion said:
roli,

The tester will have access to (and control of) the dft_tst<2:0> which is the input to the combinatorial logic that controls the internal "scanmode" signal

Would you have the DFT Compiler command that ensures that the internal "scanmode" signal is recognised as such by DFT compiler?

Thanks
animotion
Click to expand...
Yes , assuming you define precisely (in DFTAdvisor) the exact combinatorial equation of "dft_tst<2:0>" which produces 'scanmode'.
 

roli,

I am using Synopsys DFT Compiler (in Design Compiler).
I am unaware of DFTAdvisor.

The command that I am using to get DFT compiler to recognize the internal scanmode signal is:

set_dft_signal -type TestMode -hookup_pin <hierarchical location of the gate that drives the scanmode signal> -active_state 1

This is not working and causes a scan chain violation which says that the chain is broken. The only problem is the internal scanmode signal.

Can you suggest how to improve this command or another command?

Regards,
Paul

Added after 1 minutes:

Roli,

The exact combinatorial equation of "dft_tst<2:0>" which produces 'scanmode' is 111.

-animotion
 

I am sure that there is a command u can use. U mean the signal is generated by the other logic and control the whole chip to into scanmode?
I think u could set the signal to 111 (than the chip will be set in the scan mode). the command will be set_dft_signal -constant or test_hold something like that , u can search them using the keyword in the Synopsis DC reference doc.
 

I used DFTAdvisor. The command is like:

1. add primary input /.../../scan_mode
which pulls out your internal signal and treats it as primary input

2. setup scan insertion -ten /.../../scan_mode -active high
which defines that signal to be your scan_mode

I believe DFT Compiler has the similar commands.
 

set_dft_drc_configuration -internal_pins enable
 

Hi, I met the same questions:
Is the problem solved by using any synopsys dc_shell's commands?
 

joder said:
Hi, I met the same questions:
Is the problem solved by using any synopsys dc_shell's commands?
Click to expand...

Hi,
Do we have a solution to this?
What is the right way in DFTC to define an internal combo gate output pin as the scan enable?
 

Hi All,
For DFT-Compiler using DC-Shell following the command;
set_dft_drc_configuration -internal_pins enable
set_dft_signal -type constant -view existing_dft -hookup_pin <internal_hier>/scan_mode -active_state 1

Regards,
-Mukesh-
 

Hello Mukesh,

Can you provide like below command without specifying any top level pin name?
set_dft_signal -type constant -view existing_dft -hookup_pin <internal_hier>/scan_mode -active_state 1

I think, it should be like :
set_dft_signal -view existing_dft -port gpio6_from_pad -type ScanEnable -active_state 1 -test_mode all
set_dft_signal -type constant -view existing_dft -port {Top_level_port_name }-hookup_pin <internal_hier>/scan_mode -active_state 1.
You must need to define Scan enable type, thn only dc can understand that this pin as scan enable.
This command will hook up with top level port to internal scan enable.

Hope it helps

Thanks & Regards,
Maulin
 

Hi Maulin,
Yes you can pass the command as I mentioned. This is a scenario where you don't have any specific port at top-level for scan_mode/test_mode.
In that case one can have an internal logic which decides the scan_mode, and in that case you don't need to pass a top_level_port.
Yes you need to enable the a switch which I mentioned, without which DC will not consider your set_dft_signal command.

Regards,
-Mukesh-
 

Hello Mukesh,

Thanks for information.
But if you set internal node as Test mode, Than what comes into SPF? In spf, test mode is there, SPF contain only top level port constraints and other procedures, you can not define internal pin as test mode in SPF.
So for that, we need some controllability over the internal net which is used as test mode.
So can you please tell me that in you suggestion, How SPF generated?

Hope it helps.

Thanks & Regards,
Maulin
 

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