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Verify a dictionary-order permutation streamer

MediumStreaming AlgorithmsSystemVerilog

Verify a single-request block that accepts one to seven distinct bytes and streams every permutation in lexicographic order while requests and responses may stall independently.

Starting point

Question code

interface perm_if #(int N=7)(input logic clk);
  logic rst_n, req_valid, req_ready;
  logic [3:0] count;
  logic [7:0] item[N];
  logic out_valid, out_ready, out_last, out_error;
  logic [7:0] permutation[N];
  logic [3:0] out_count;
endinterface
Reviewed example

Work through one case

Input
accepted distinct bytes=[b,a,c]
Expected output
[abc, acb, bac, bca, cab, cba]

Sorting the captured frame establishes the first lexicographic permutation; successive next-permutation steps produce all 3! results.

What to cover

Requirements

  1. For a legal count, deep-copy and sort the accepted bytes, then expect exactly count-factorial permutations with unused lanes zero.
  2. A duplicate byte or count outside 1 through 7 produces one final zero-payload error beat and no successful permutations.
  3. Keep req_ready low until the final response handshake; bound the first beat, inter-beat gaps, and total completion when out_ready is high.
  4. Require stable stalled output, out_last only on the final item, and complete cancellation on reset.
Continue practicing
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