shift.v

一个桶形移位寄存器的.v文件

`timescale 1ns/10ps
module shift(
				//input
				clk,
				rst,
				s,
				in,
				//output
				out);
input clk,rst;
input [3:0]s;
input [7:0]in;

output [7:0]out;

reg [7:0]vol;

assign out=vol;

always @(posedge clk)
begin
  if (!rst)
  	vol<=8'h0;
  else
  	begin
			if(s==4'h0)
				vol<=vol;
			else if (s==4'h1)
			  vol<={in[6:0],1'b0};
			else if (s==4'h2)
			  vol<={in[5:0],2'b0};
			else if (s==4'h3)
			  vol<={in[4:0],3'b0};
			else if (s==4'h4)
			  vol<={in[3:0],4'b0};
			else if (s==4'h5)
			  vol<={in[2:0],5'b0};
			else if (s==4'h6)
			  vol<={in[1:0],6'b0};
			else if (s==4'h7)
			  vol<={in[0],7'b0};
			else if (s==4'h8)
			  vol<=in;
			else if (s==4'hf)
			  vol<={1'b0,in[7:1]};
			else if (s==4'he)
			  vol<={2'b0,in[7:2]};
			else if (s==4'hd)
			  vol<={3'b0,in[7:3]};
			else if (s==4'hc)
			  vol<={4'b0,in[7:4]};
			else if (s==4'hb)
			  vol<={5'b0,in[7:5]};
			else if (s==4'ha)
			  vol<={6'b0,in[7:6]};
			else // (s==4'h9)
			  vol<={7'b0,in[7]};
		end
	
end			

always @(negedge rst)
begin
	vol<=8'h0;
end
	
endmodule