Description about how the circuit works & how we can write alp for this

simple digital clock using 8051 microcontroller at89c51 pdf

Digital clock displays the time using numbers. This circuit is used in many applications like cars, railway stations, houses, offices, etc. in order to provide accurate time and date. In this type of applications, normally we use RTC (Real Time Clock) ICs to display the time and date accurately. This circuit displays the time on LCD. For this clock, we can set the time at any instant. Here the clock works in 24 hour mode and the RTC chip is configured by programming 8051 controller.

Circuit Principle:

Here 8051 controller continuously reads the data from Real time clock and process it in correct order to display the time on LCD. INT1 of the 8051 controller is used to set the time to the digital clock. If you make P3.3 pin LOW then interrupt arises and set_time function is called to set the time. To set the time to the clock use P1.4 and P1.5 pins. P1.4 is used to vary the hours and P1.5 is used to vary the minutes. After setting the time make P1.6 high to run the clock with the time set by user.