Hardware interview practice
Procedural stall-stability checker
At each clock, report an error when the previous cycle was stalled and current valid drops or the payload changes.
Reviewed example
Work through one case
Input
previous cycle: valid=1, ready=0, payload=0xA4; current valid=1, payload=0xA5Expected output
report a protocol error, then save the current handshake and payload for the next checkThe prior stalled cycle owns the stability obligation. A four-state comparison catches the change before the saved sample is updated.
What to cover
Requirements
- Track the previous valid, ready, and payload values.
- Use four-state comparison.
- Check before updating the saved sample.