Description: traffic signal control : 1. A parallel port by 8255 to control the LED light emitting diodes-destruction. 2. A red light population control, population control yellow B and C population control green. 3. Output-0, the output of a destruction. 4. Use 8253 to control transform regular time. Requirements : there is a crossroads, 1,3 to the south, to the north, the east-west direction 2,4. Initial state for four junctions in the whole bright red light. After 1,3 junctions green light, red light junctions in the 2,4-, 1,3 junctions opening direction. Delayed 30 seconds after the green light junctions 1,3 out and the junction of 1,3 begin blinking yellow light (1HZ). Stars 5, 1,3 junctions in the red light, green light junctions in the 2,4-, 2,4 direction was opened to traffic junctions. Delayed
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