always @(posedge sys_clk or negedge sys_rst_n) begin
if(!sys_rst_n)
led <= 4'b0000;
else
case(key)
4'b1110: led <= 4'b0001;
4'b1101: led <= 4'b0010;
4'b1011: led <= 4'b0100;
4'b0111: led <= 4'b1000;
default: led <= led;
endcase
end
always @(key or sys_rst_n) begin
if(!sys_rst_n)
led = 4'b0000;
else
case(key)
4'b1110: led = 4'b0001;
4'b1101: led = 4'b0010;
4'b1011: led = 4'b0100;
4'b0111: led = 4'b1000;
default: led = led;
endcase
end