dft signals - synopsis

[ee1]

Hi,
Can someone please explain to me what is the meaning of the options: "existing_dft" and "spec"? in the set_dft_signal command?
(its hte options of "-view" flag)

Thanks!

 

[ranger01]

existing --> the signal is already defined as port in the rtl.
spec --> defining the new port and adding to the netlist.

somtimes designer might have included dft test points in the rtl . In that case scanmode or testmode signal will be defined as ports in the rtl. While defining the DFT architecture you just have to mention that dft signal is already "existing" in the rtl

 

[ee1]

10X,
So if all my dft signals are already defined in rtl, tey all should be "existing_dft"?
BTW, if i define a signal as "spec" and he allready exsist in my rtl, would it be wrong and give me errors/violations? or it will just not be created?

 

[ranger01]

10X,
So if all my dft signals are already defined in rtl, tey all should be "existing_dft"?

Yes.

BTW, if i define a signal as "spec" and he allready exsist in my rtl, would it be wrong and give me errors/violations? or it will just not be created?

If the signal already exists and you try to "create_port" then it will give error saying the port already exists. Instead, without creating the port you define the dft signal with spec then it will not give you error. But in both cases the dft test points in rtl will not function as intended.