Below it i have implemented a Reset circuit, it is basically an AND gate that sends a high signal to the reset pin of the Flip Flops if the output of the counter is a 1010 or a 10 in decimal. Therefore we produce a Binary number equivalent to the number of cycles of the input clock signal.Īs shown above, to the left is my circuit that makes the 4-bit up counter for the 1's place. This is important because for each 2 toggles of the first FF a toggle is produced in the consecutive FF and so on until the last one. The idea is that if we send a high signal to the 'J' and 'K' inputs of the FF, the FF will toggle its state at each cycle of the input clock. I use an asynchronous counter (also called a ripple counter). There are 2 types of counters, a synchronous counter (where the clock is connected to all FF) and an asynchronous counter where the clock is fed to the first FF and the output acts as the clock of the next FF. The second part is a 3-bit up counter that counts up to 6 which makes up the 10's place of the seconds. The first part is a 4-bit up counter that counts up to 9 which makes up the 1's place of the seconds. However on a breadboard feel free to build the circuit i have above or use a DS1307 module. I just used a 1 Hz pulse generator to speed up the Simulation time in Multisim. By that same token if we chain 15 Flip Flops we can divide the input signal frequency to get our 1 Hz signal. The reason that is important is because a J-K flip flop output Toggles at the Positive or Negative edge (depends on the FF) of the input signal, therefore the output is effectively at a frequency that is half of the original input. The reason 32.768 kHz is used is because it is higher than our maximum hearing frequency which is 20 kHz and it is equal to 2^15. One way we can generate a 1 Hz signal is by using a crystal oscillator circuit that generates a 32.768 kHz signal (like the one i designed above which is called a pierce oscillator), that we can then divide by using a chain of Flip Flops. in the next steps we will see how we can count those cycles to make up the seconds, minutes and hours of our clock. a 1 Hz clock is generating a pulse every second.

The Concept behind a Digital Clock is that we are essentially counting up clock cycles.

Jk flip flop in multisim