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What is CRPR (clock reconvergence pessimism removal)?

A correction in OCV-based STA that adds back to the slack the difference caused by applying both slow and fast factors to the shared portion of the launch and capture clock paths. The shared portion is physically the same, so it cannot be both slow and fast within one clock edge.

Japanese name: CRPR(共通パスの悲観性の除去)

CRPR (clock reconvergence pessimism removal) appears in 1 practice question across 1 topic, including Timing analysis and CDC.

Field: Timing analysis and CDC

Try it: questions about CRPR (clock reconvergence pessimism removal)

In STA with OCV derating, when the launch and capture clock paths share a common portion, which correctly describes CRPR (common path pessimism removal)?

  1. AIt treats the delay of the common portion as zero and recalculates the clock arrival times
  2. BIt removes the impossible extra pessimism caused by applying separate slow and fast values to the common portion
  3. CIt applies an even larger derating factor to the common portion to stay on the safe side
Show answer and explanation

Answer: B. It removes the impossible extra pessimism caused by applying separate slow and fast values to the common portion

OCV estimates the launch clock path as slow and the capture clock path as fast, but the common portion from the root to the branch point is physically the same buffers and wires, so it cannot be both slow and fast within a single edge. If the common portion has a delay of 1.0 ns and the factors are 1.1 and 0.9, the 0.2 ns difference between 1.1 ns and 0.9 ns is extra pessimism. CRPR adds this difference back to the slack, bringing the result closer to reality. It does not set the common delay to zero, and enlarging the factor is the opposite operation.

CRPR (clock reconvergence pessimism removal) in the explanations

Questions that mention CRPR (clock reconvergence pessimism removal) (1)

  1. In STA with OCV derating, when the launch and capture clock paths share a common portion, which correctly describes CRPR (common path pessimism removal)?

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Related terms

STA (static timing analysis) OCV (on-chip variation) Derating Slack Asynchronous FIFO Clock domain Clock uncertainty Critical path False path Handshake

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