A digital clock is 1 that displays time digitally. The circuit explained here displays time with two ‘minutes’ digits and two ‘seconds’ digits on four seven segment displays. The seven segment and switches are interfaced with 8051 microcontroller AT89C51. This circuit may be used in vehicles, houses, offices and many others. The moment the Vcc supply is supplied to this circuit, the clock begins from 00:00. Time is displayed on four 7 segments (in frequent anode configuration) by utilizing the notion of multiplexing. That is reached by utilizing timer interrupt (Timer0) of AT89C51 which is configured to refresh 7 segments. The segments are refreshed numerous periods in the 2nd for simultaneous show. The clock runs which has a delay of precisely a single 2nd. Timer1 is used to produce a time delay of a single second. The info pins (a-h) of the many segments are interconnected and get signal from port P2 in the microcontroller. The control or allow pins (popular anode) are connected to pins 1-4 of port P1 (P1^0 - P1^3).
The number on 4th section (displaying the unit digit of 2nd) is incremented as soon as in the 2nd since it goes from 0 to nine. The range on 3rd section is incremented just after every 10 seconds from 0 to 5. Hence seconds are displayed different from 00 to 59. The digit to the 2nd section variations after every 60 seconds (a minute) from 0 to nine etc. So the clock runs for an hour and following that it resets to zero once more
source:engineersgarage.com
