Non-blocking assignment

// this implements 3 parallel flip-flopsalways @(posedge clk) begin B = A; D = C; F = E; end

// this implements a shift registeralways @(posedge clk) begin B <= A; C <= B; D <= C; end

// this implements a shift registeralways @(posedge clk) begin {D, C, B} = {C, B, A}; end

• Non-blocking assignment is also known as RTL assignment

  • If used in an always block triggered by a clock edge
  • Mimics register-transfer–level semantics: All flip-flops change together

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