How to design a 2 bit counter using D Flip-Flop(7474)?

Answer 1

There are 2 ways.
1. Ripple Counter
Tie the ~Q output of each flip-flop to it's respective D input (turns them in to type T flip flops).
Tie the LSB Q output to the clock input of the MSB flop.
Clock the LSB clock input to count.

2. Synchronous counter
Tie the LSB ~Q to it's D input.
Connect the MSB ~Q and the LSB Q to the inputs of an AND gate.
Connect the output of the AND gate to the D input of the MSB.
Connect the clocks together.

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Answer 2

7474 D Flip Flop

Answer 3

D(a million,0):=Q(a million,0)-a million If i wanted to spend the time i ought to supply you the combinational good judgment, yet as we talk an engineer shall we the compiler try this. it would be something like: D(0):= no longer Q(0) D(a million):= no longer(Q(a million) XOR Q(0))