`default_nettype none module top(i_clk, jmp, in, out); parameter DEFINED=5; input wire i_clk, in, jmp; output reg [8-1:0] out; initial out = 0; always @(posedge i_clk) if (jmp) out <= { out[UNDEFINED-1:0], in }; else out <= { 1'b0, out[UNDEFINED-1:1] }; endmodule