Hardware interview practice
Check ordered grants for overlapping requests
Request pulses may overlap. Queue up to eight accepted request IDs and require one ordered grant per request within 1 through 15 clocks.
Starting point
Question code
input logic clk, rst_n, req, grant;
input logic [7:0] req_id, grant_id;Reviewed example
Work through one case
Input
req A at cycle 2, req B at 3, grant A at 5, grant B at 8Expected output
pass; A retires at latency 3 and B retires at latency 5The FIFO binds each grant to one oldest request, preserving order even while requests overlap.
What to cover
Requirements
- Store each accepted request ID and issue cycle.
- Compare each grant only with the queue front; a wrong-ID grant reports an error without retiring that request.
- Flag zero or excessive latency, wrong order, overflow, and unsolicited grants.
- Report and retire a timed-out front request once so later obligations can still be checked; reset clears every pending obligation.