The function of a lock-up latch

[rakeshnunna]

Hi,
A lockup latch is used to prevent data corruption caused by overwriting of new data over the present data before the clock edge occurs.

i.e there is a potential problem of data coming early and overwriting the present actual which has to be fed.

This can be prevented by placing a lock up latch with negative level sensitive D latch connecting the two different chains

 

[funzero]

lockup latches

DFTC can automated add a lockup latch when your design is multiple clocking .

 

[akrlot]

lock-up latch

thx all.I used the following command to stitch the chains and automatically create a lockup lach:
set_scan_configuration -clock_mixing mix_clocks

 

[roger]

lockup latch

hi;
could you explain why a lockup latch is inserted between scan chains with different clocks? and how to stitch two scan chains using a latch with DFTC?
thx

see material on this page

 

[xworld2008]

lock up latches

Lock-up latches are necessary to avoid skew problems during shift phase of
scan test. These problems occur if FF’s driven by different clock lines are
connected within a single scan chain.
For this it is recommended to separate scan chains according clock domains.
If not reasonable lock-up latches have to be inserted into the scan chain. To
allow a smooth scan chain stitching on product level it is recommended to
finish each core level scan chain by a lock-up latch.