why to use multiple lockup latches and how?

[deepen talati]

Sir why it is required to use multiple lockup latches and what is the case if scan chain contains both LE and TE flops? Then how lockup latches solves problem?

 

[chiranjeevinaidu]

Hi
lockup latches are used scan based design for hold timing closure of shift modes.

where clock skew is large and meeting the hold timing is big challenge due to uncommon path,that is why lockup latches are used to connect two flops in scan chain having excessive clock skews/uncommon clock paths as the probability of hold failure is high in such cases..
launch flop and capture flops having two different clock domains .......

Regards
chiranjeevi