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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
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