When should DFT come into the flow?

[dftguy]

Suppose we have a project starting. When should DFT come into the flow. What is the strategy that should be followed from starting in details? Any related document would also help.

 

[somu.atluri]

DFT Strategy

You should ideally start at RTL level.
You have to decide if you would like to do full scan or partial scan. And, you need to decide on number of scan chains and number of test modes.

Also, depending on number of memories & frequencies, you have to take decision on the
1.MBIST controller and algorithms
2. or if you have less memory and you have a CPU, you can go with CPUBIST.

If any third party IPs, then you have to discuss with them about the scan and memory patterns (if any).
1. If the IP vendor does accept to deliver patterns for the IP, then you need to have a test mode for those patterns and muxing logic to mux it with the IO pads (the ones used for SoC SIs, SOs)
2. else, you need to get information about the clocks and other test related information(like memories and its frequency), so that you can develop your test logic well before the final delivery of IP.

Also, you need to generate the boundary scan and jtag module for the SoC. Depending on the number of IPs you have in design, you need to take a decision on using P1500 (embedded core test).

you need to decide on the compression logic, depending on the scan chain length.

And from the testing perspective, you have to take following desicions
1. which pads you want to use for testing (also dedicated or multiplexed)
2. Decision needs to be taken on the number of pins that can be connected to the tester. Based on this, the test engineers will plan for multisite testing (this is mostly done at architecture level)


I might be missing some points.

 

[visualart]

DFT Strategy

you may insert the dft scan chain after the synthisis.
do test synthesis, and generate the partterns for test.

BRs