[DFT] Posedge & Negedge flops stiching

[ivlsi]

Hi All,

How to stitch a couple of negedge flops in the design where most of the flops are posedge?

How to balance chains where only few flops are negedge but most flops are posedge?

Is it possible to combine posedge and negedge flops in the same chain?

Thank you!

 

[ivlsi]

[DFT] Clocks balancing

Hi All,

What techniques are used for clocks balancing in DFT?

Thank you!

 

[maulin sheth]

Hello,
yes, we can stitch +ve edge followed -ve edge flops in same scan chain. It will not create any issues.
But you can not connect -ve edge followed by +ve edge flops as its violating the shift path that you can check by doing timing analysis.

 

[ivlsi]

Could you explain more please - why +ve edge followed by -ve edge flops will not create timing violations on the shift path while the -ve edge followed by +ve edge flops will do create such violation?

 

[maulin sheth]

There are so many links available on internet. Can you please check there? Do google like : Lock up latch in DFT. Because It is quite difficult to understand here.
You can do small exercise like :
1. Draw a 4 scan flop sequence. Do timing analysis with waveforms.
Do like - if first 2 are +ve edge and last 2 are -ve edge and vice versa. If you do for shifting only, you will get better understanding.

Let me know if any doubt.