PIC Traffic Lights

  
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All that remains now is for the code to be `, compiled and converted to a HEX file that the PIC can understand. This is achieved easily with the PIC compiler that comes with the PICBASIC package. The PIC is programmed with any of the parallel or serial port programmers that are available free of charge from the NET. If you arrange the LEDs as the
PIC Traffic Lights - schematic

diagram of my prototype box, FIG 1, then the LEDs at the left of the PIC we will call LEDs A and to the right of the PIC LEDs B. Number them, starting at the top of LED A the RED LED number 0. The next one down is AMBER and is number 1. The bottom one GREEN is numbered 2. The right hand side LEDs starting from the top is numbered 4 for the top RED LED with number 5 being allocated for the middle, AMBER LED. The bottom, GREEN LED is number 6. Loop: Is the start of this programme. It is suitably called loop, as that is what the programme does. It loops continuously until it is switched off. It must be followed by the colon. HighO: Places a logicl on portB pinO consequently lighting LED 0. The colon is there to separate the first statement (high 0) from the next one in the same line. If the next statement (high 6) was placed on the next line down there would be no need for the colon. It just saves space. Pause1000 Is an instruction to tell the PIC to delay for 1 second. The actual time will depend on the clock frequency of the PIC. As a rule of thumb 1000 can be regarded as 1 second and 5000 as 5 seconds. The portB pins are placed in a register called bl. This could have been called b0, b2, b3 etc. there are, of course, only so many of these registers in each PIC. Lowbl instructs that everything in register b 1 goes to logic 0. In our case all the pins in portB, 0 to 7 are taken low. It does this in sequence from pin 0 to pin...



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