Design And Construction Of A Digital Clock With Calendar

    Counting unit;
Each unit of the clock is linked to a general purpose register for counting purposes. There is a routine program that handles counting up for each of the clock units (refer to appendix for codes of routine program). The time taken for each increase is determined in the routine handling it. The output of each counter is binary and therefore needs to be converted to seven segment display format. Another routine is program to handle this (refer to appendix for routine program).
    Display decoder;
The display decoder is a program that converts binary coded decimal output of the counter to seven segment display format. The output of each counter is converted to numeric display equivalent using this decoder.
    Scanning unit;
In this project, the required number of terminals required can be estimated as follows;
Each 7 segment requires at least 7pins of the MCU, there are ten 7 segments in the circuit, therefore required pins of the MCU is 7 * 10 = 70 pins. Other pins required for proper functioning of the MCU are the 4 power supply pins, 2 oscillator pins, 1 MCLR pin making the total number of pins required = 70 + 4 + 2 + 1 = 77pins. The MCU has just 40pins and not all these pins are available, therefore there is need for the LEDs and the seven segments to be multiplexed (discussed in the next chapter). There is a routine that handles this part of the display in the program (refer to appendix).