Design And Construction Of A Digital Clock With Calendar

CHAPTER TWO
3.0    LITERATURE REVIEW
This project is an embedded system that uses a microcontroller to achieve the required functions. This device operates by running a software program burn into its flash memory, this is divided into loops, and each loop has it specific function. These loops are labeled counter, decoder and display scanner.
In this project, I have built a digital clock with 24 hour count time. The clock runs from 00:00 to 23:59 and then back to 00:00. The display has two four digits, two digits for minutes and two for hours. Six displays for the date and year.   The specialty of this clock is that it has very low power consumption and condensed layout.
This device used some general purpose registers as 0-9 counter for the unit’s digit of minutes display and also for the 0-5 counter of the ten’s digit of minute. Some of this registers were also use for the unit’s digit of hour, and the 0-9 counter, for the ten’s digit of hour. Other than this, some of the remaining registers were been program to ensure proper functioning of the clock.
There is only one clock input for the entire system, the clock input into the 0-9 counter used for the unit’s digit of minute. The clock inputs for the other blocks are derived from the output of the previous blocks as shown in the block diagram for the system. We have a total of eight seven segment displays.
Every 0-9 counts, we add one on the ten’s digit of minute. After every 6 such cycles, we add one on the unit’s digit of hour, and every 10 hours, we add one on tens digit of hour. As soon as it reaches 2 on the ten’s digit of hour and 4 on unit’s digit of hour, both the ten’s.
And the unit’s digits of hour are reset to 0. So, in practice, we do not see 24:00 displayed. We rather see a transition from 23:59 to 00:00. The day’s counter is increased. The maximum count by the day counter is determined by the month’s present value. When the months count is ‘2’(February), the maximum count available to the day counter is 28, when it is April, June, September, November i.e. ‘4,6,9,11’ maximum count is 30 days, when it is ‘1,3,5,7,8,10,12’ the maximum count by the day counter is 31.