lfsr_updown.v

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`define WIDTH 8
module lfsr_updown(
clk,           //Clock input
reset,         //Reset input
enable,        //Enable input
up_down,       //Up Down input
count,         //Count output
overflow       //Overflow output
);

input clk;
input reset;
input enable;
input up_down;

output[`WIDTH-1:0]count;
output overflow;

reg[`WIDTH-1:0]count;

assign overflow=(up_down)?(count=={{`WIDTH-1{1'b0}},1'b1}):(count=={1'b1,{`WIDTH-1{1'b0}}});

always@(posedge clk)
if(reset)
	 count<={`WIDTH{1'b0}};
else if(enable)begin
	  if(up_down)begin
	  	count<={~(^count&`WIDTH'b01100011),count[`WIDTH-1:1]};
	  end
	else begin 
		  count<={count[`WIDTH-2:0],~(^(count&`WIDTH'b10110001))};
	end
end
endmodule