embded

Hello again! in the first part we've seen how the basic 24h clock works (the hour coulmn counts to 24 and then resets to 00). It was quite easy and there were no problems, but let's extend the idea a little bit. What if we want to design a 12h clock?  well.. it's the same idea but there was a little problem which is: when the hours reachs 12 and counts to the end of the hour 12.59 we don't want it to reach 13, we rather want it to reset to...? 01 not 00 so i had to make a small trick you'll see later. How the circuit works? It's the same circuit as the first part   but we've to edit the hours coulmn so it resets to 00 when it reachs 13 and then clocks the first coulmn of hours so it becomes 01 .. simple! So that's how i made it , the two AND gates U9 and U10 detect the case when the hours coulmn is 13 and their output(A) then will be 1.  Output A has two jobs to do : - The first is to reset the boths hours coulmn so it's