DFT : querry on compression

[abc_81]

Hi ,
How to decide compression ratio ? what is the limitation on compression ? will it affect coverage ?
Is there any generic architecture for compression ? please provide good document on scan compression

 

[rca]

For fastscan, the tool provides the compression ratio without coverage reduction.
Normaly, the compression engine is tool dependant, I means, you need to have the licence to generate the "RTL code" of the compression engine and the licence to generate the patterns.

 

[abc_81]

We are using testkompress tool for compression. If I use this tool and if I know the area(flop count), how do I calculate the compression ratio ?

 

[rca]

what we did, with tessent/fastscan, just load the netlist as usually, and there is a command to analyze the compression ratio optimum for the design.
based on that you could generate the kompression engine.
The compression ratio could be just to reach a ATE time, without looking to be at the "optimum" point.

for secure way (in case kompression issue) and design constraint, in a previous design, we have four scan modes:
1- 2 scan chains without compression (bypass mode)
2- 2 scan chains with compression with 384 internal scan chains
3- 8 scan chains without compression (bypass mode)
4- 8 scan chains with compresion with 384 internal scan chains

 

[samuraign]

what we did, with tessent/fastscan, just load the netlist as usually, and there is a command to analyze the compression ratio optimum for the design.
based on that you could generate the kompression engine.
The compression ratio could be just to reach a ATE time, without looking to be at the "optimum" point.

for secure way (in case kompression issue) and design constraint, in a previous design, we have four scan modes:
1- 2 scan chains without compression (bypass mode)
2- 2 scan chains with compression with 384 internal scan chains
3- 8 scan chains without compression (bypass mode)
4- 8 scan chains with compresion with 384 internal scan chains

Hi,
Can you share the command for analysis

 

[maulin sheth]

In synopsys, We have analyze_compressor command in TetraMAX.