Traffic Light

8051 MICROCONTROLLER BASED EXPERIMENT (SIMPLE CONTROL APPLICATIONS)

                                                                               TRAFFIC LIGHT CONTROLLER

AIM:

            To write an assembly language program to control the traffic light signal using the microprocessor 8085

APPARATUS REQUIRED:

                                    8051 kit, power chord

THEORY:

                        A simple contraption of a traffic control system is shown in the figure where the signaling lights are simulated by the blinking or ON – OFF control of LED’s.  The signaling lights for the pedestrian crossing are simulated by the ON – OFF control of dual colour LED’s.

                        A model of a four road – four lane junction, the board has green, yellow and red LED’s which are the green, orange and red signals of an actual systems. 12 LEDs are used on the board.  In addition 8 dual colour LEDs are used which can be made to change either to red or to green.

                        The control of the LEDs is as follows:

                        The board communicates with the microprocessor trainer by means of a 26 core cable which is connected to the output pins of any parallel port of trainer.

                        The outputs (i.e. port) are the inputs to buffers 7406 whose outputs drive the LEDs.  The buffered output applied to the cathode of the LEDs decides whether it is ON or OFF.                   

  

4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 410A 410B 410C 410D 410E 410F 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 411A SUBROUTINE 411B 411C 411D 411E 411F 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 412A 412B 412C

21 00 45 0E 0C 7E D3 0F 23 7E D3 0C 23 7E D3 0D CD 1B 41 23 0D C2 09 41 C3 00 41 C5 0E 05 11 FF FF 1B 7A B3 C2 21 41 0D C2 1E 41 C1 C9

START LOOP1 DELAY LOOP3 LOOP2

LXI MVI MOV OUT INX MOV OUT INX MOV OUT CALL DELAY DCR JNZ JMP PUSH MVI LXI DCX MOV ORA JNZ DCR JNZ POP RET

H, 4500 H C, OC H A, M OF H H A, M OC H H A, M OD H DELAY H C LOOP 1 START B C, 05 D, FFFF D A, D E LOOP 2 C LOOP 3 B

Initialize the HLReg. Pair to 4500 H Initialize the count Reg.  C to OC H Initialize the ports of 8255. Send the data to switch ON / OFF The LED’s through port A. Switch ON / OFF the LED’s through port B Call the subroutine delay Get the next data and decrement the count. If the count is not zero go to instruction labeled “LOOP 1” Jump unconditionally to the instruction labeled “START” Save the contents of BC Reg. Pair to stack pointer. Initialize Reg. C to hold data 05 H. Get the data FFFF H in DE Reg. Pair. Decrement the content of DE Reg. Pair Check whether the contents of DE Reg. Pair is zero. If the contents of DE Reg. Pair is not zero go to instruction labeled LOOP 2 Decrement the content of Reg. C If the contents of Reg. C is not zero go to instruction labeled “LOOP 3” Move the contents of stack pointer to BC Reg. Pair Return to the main program.

RESULT:

Thus an ALP  to control the traffic light signal was written and executed.