updown_count.v

verilog_hdl教程135例

module updown_count(d,clk,clear,load,up_down,qd);
input[7:0] d;
input clk,clear,load;
input up_down;
output[7:0] qd;
reg[7:0] cnt;
assign qd = cnt;

always @(posedge clk)
begin
if (!clear)  		cnt = 8'h00;
else  if (load)  	cnt = d;
else  if (up_down) 	cnt = cnt + 1;
else  			cnt = cnt - 1;
end
endmodule