void _delay_loop_2(uint16_t __count)
Delay loop using a 16-bit counter __count, so up to 65536 iterations are possible. (The value 65536 would have to be passed as 0.) The loop executes four CPU cycles per iteration, not including the overhead the compiler requires to setup the counter register pair.
Thus, at a CPU speed of 1 MHz, delays of up to about 262.1 milliseconds can be achieved.