Direction, 2 and 4 are east and west, and the initial state is that the red lights at four intersections are all on. After that, the green light at 1 and 3 intersections is on.
The red light at intersections 2 and 4 is on, and the direction of intersections 1 and 3 is open to traffic. After a time delay, the green light at 1 and 3 intersections goes out, while 1,
The yellow light at the intersection began to blink. After several flashes, the red light at 1 and 3 intersections is on, and the green light at 2 and 4 intersections is on.
The direction of intersection 4 is open to traffic. After a delay, the green lights at intersections 2 and 4 went out and the yellow lights began to flash. Blinking if
After finishing the time, switch to the intersection direction of 1 and 3. After that, the above process is repeated. For each set of lights on and off, we use
It is the input and output function of 8255A.