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How to wrap a black box with Synopsys Shadow LogicDft ?

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akrlot

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shadow logic in dft

hi;
i want to wrap a black box (memory block) automatically with synopsys Shadow
LogicDft utility. what's the flow and commands i need?
thx
 

difficult dft question

i don't think memory bank need DFT. it uses BIST for memory
 

    A

    akrlot

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    htung22

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Re: difficult dft question

You are right.but the wrapper i want to add will better the test coverage of the BIST.any suggestions?
 

difficult dft question

i haven't used the tools you mentioned, but

as far as i know, the MBIST can get very good coverage depends on what algorithm you choose.

i think you confuse it with LBIST (logic BIST), no scan chain can get into it, and i don't believe you wrap the port will add any good
 

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    akrlot

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Re: difficult dft question

i mean the test coverage of the bist itself not the coverage of the DUT.
The black box has unobservable inputs and uncontrollable outpus and
this can be fixed automatically by Shadow logicDft by inserting test points around
the black box
 

Re: difficult dft question

I haven't used that kind of tools. But I don't think it is difficult to wrap the black box manually. It is simply a multiplexer controlled by scan_enable on each input and output pin of that black box. You may write the wrapper module in RTL very easily.
 

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    akrlot

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difficult dft question

Memory BIST controller circuit might NOT need to be scaned, since the controller ckt failed.... then the BIST test fail.

You will catch the failure in the BIST test, why do you waste your gate count in scan?
 

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    akrlot

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Re: difficult dft question

If tell ATPG tool the memory model. The tools may set certains state at memory outputs from its inputs. In this way the shadow logic can be tested. However, it is riskey. You need verify the model and if the tool working correctly.
 

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    akrlot

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Re: difficult dft question

you have installed the tools ,you must have reference document.
Wrappering memory is typical ref flow in the document.
 

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    akrlot

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difficult dft question

I think that MBIST is all your need. No body test all faults, just wish to test the optimum.
 

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    akrlot

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Re: difficult dft question

first probably using set_scan_configuration to define the scan specification , which includes the shadow logic insertion ( sorry for forgetting the detail switchs, u can refer to the man set_scan_configuration), then using insert_dft, this command will insert shadow logic aside scan. There is a detail guide in SOLD doc , dft compiler user guide
 

difficult dft question

set_dft_configuration -shadow_wrapper
set_wrapper_element [get_cell -hier your_ram] -type shadow
set_port_configuration -cell your_ram -port D -write {WEN 0}
set_port_configuration -cell your_ram -port Q -read {WEN 1}
insert_dft
 

Re: difficult dft question

sunspot said:
set_dft_configuration -shadow_wrapper
set_wrapper_element [get_cell -hier your_ram] -type shadow
set_port_configuration -cell your_ram -port D -write {WEN 0}
set_port_configuration -cell your_ram -port Q -read {WEN 1}
insert_dft
Click to expand...

Where these commands will used? dc?
 

difficult dft question

yes, you can type these commands in dc_shell-t
or edit a file including these commands and then
dc_shell-t -f commands.scr
 

Re: difficult dft question

sunspot said:
yes, you can type these commands in dc_shell-t
or edit a file including these commands and then
dc_shell-t -f commands.scr
Click to expand...

so these command are planted inDFT compiler?
 

difficult dft question

yes, DFT compile can automatically add shadow logic auto fix logics.
 

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