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Hardware interview practice

Constrain a Gray-adjacent sequence

MediumConstraintsSystemVerilog

Randomize 16 unique 4-bit values starting at zero so each adjacent pair differs in exactly one bit.

Reviewed example

Work through one case

Input
randomize 16 unique 4-bit values with values[0]=4'b0000
Expected output
One valid result: [0000,0001,0011,0010,0110,0111,0101,0100,1100,1101,1111,1110,1010,1011,1001,1000]

This complete Gray path visits every 4-bit value once and each constrained adjacent pair has Hamming distance one; the last-to-first transition is not constrained.

What to cover

Requirements

  1. Fix the first value at 4'b0000.
  2. Require a Hamming distance of one between neighbors.
  3. Use every 4-bit value at most once.
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