Design of a Digital Clock and Stopwatch with Seven-Segment Display Using a Microprocessor Training Kit

Digital clocks and stopwatches are small real-time systems that combine timing, counting and display multiplexing. This paper presents the design of a digital clock and stopwatch with a multiplexed seven-segment display using a microprocessor training kit. Time is kept in binary-coded decimal, updated from a timing source, and shown by cyclic display refresh; keys select clock and stopwatch modes. Timekeeping accuracy and display quality are evaluated by calculation and simulation. In simulation the BCD roll-over was correct in all 5 test cases and after 48 h of simulated counting, the display was refreshed at 100 Hz without visible flicker, and the clock drift was bounded by ±1.7 s per 24 h by the crystal tolerance.