Hardware interview practice
Valid Drops During a Stall
Each column is a rising clock edge. The source drives valid and data; the receiver drives ready. Rule to apply: If valid is 1 and ready is 0 at an edge, valid must remain 1 and data must remain unchanged at the next edge. A transfer occurs only when valid and ready are both 1. What is the root cause of the protocol failure?
Choose one
Answer choices
- A. The receiver raises ready before valid.
- B. The source drops valid before the stalled beat is accepted.
- C. The source changes data while a transfer occurs.
- D. The receiver accepts two copies of the beat.