Electronics 5b - Binary counters

Question 1

What does a D-type edge triggered flip-flop look like in a circuit?

Answer 1

This one is a falling edge flip-flop. If it was just C then its a rising edge triggered flip-flop.

Question 2

What does a circuit for a shift register look like and whats its purpose?

Answer 2

Circuit shown

Explaination:
* Only carries the input along each flip-flop one after another.
* This can be useful for things lik train or bus displays that shift patterns across, to make the station signs etc.

Question 3

What is the circuit for a binary counter and how does it work?

Answer 3

Circuit shown below.

Explaination:
* In each flip-flop, it’s NOT Q input is the input in D.
* The Q output for each flip-flop depends on the input of D when it was clocked.
* Notice that the clock is a rising edge trigger flip-flop, so we only get data changes when it goes from 0 to 1 on the clock.
* So if NOT Q is origianlly 1, then D is also 1, but Q is 0, so A is 0. when the clock ticks to 1, this then changes NOT Q and D to 0, and Q and A to 1.
* This now means that for the next flip-flop, the clock is set orignally, to 0, then once it changed to 1, the NOT Q changed to 0 which was the input for the clock on the B section. This means that no data change in D for B. But once the clock goes back to 0 and 1 once more in a cycle, the NOT Q goes back to 1 and so the D value of 1 in B can be entered.
* This is why the for A (0->1) takes 1 clock pulse, B takes 2 clock pulses, C takes 4 clock pulses, D takes 8 clock pulses.
* This is why it is used for a binary counter, look at the truth table. Remember read it from right to left for binary number in this case.

Question 4

How can we make a divide by N counters circuit for everyday use?

Answer 4

The ‘divide by N counters’ works because each flip-flop connected one to the other will mean the effective frequency out, will be 2^N times less than the original clock frequency. That is somewhat how you can make digital clocks such as the one below.

Question 5

What are some uses of Sequenctial logic and binary counters?

Answer 5

Memory chips, such as RAM, DRAM or flash memory.