SKEW

• SKEW is the difference in the arrival time of the clock pulse between a source and destination register (or other synchronous element)

• Some Positive skew can be beneficial; it will decrease the required setup time:

• Too much Positive skew can create a race condition, hold-time violation:

Q

D

Q

D

Clock @ Source Register

Clock @ Destination Register

Clock skew

Clock @ Source Register

Clock @ Destination Register

Clock skew

A

B

Data “A” arrives at the destination, but it could be overridden by

Data “B”, which is meant for the next pulse at the destination reg.

If the clock pulse arrives at the source reg first followed by the dest reg, then it is “positive skew”; if it arrives at the dest followed by the source, then it is “negative skew”.

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