Counters - Starting With a Flip-Flop
Using The 74193 Counter

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        Counters are found in many places where you might not expect to find them.  Here are a few places where you would see counters.

You can see that there are many places where counters are built into equipment.  They are found in many different kinds of equipment and they are devices that you really need to know about.
The Toggle (T) Flip-flop - A One Stage Counter

        A toggle flip-flop is really a single bit counter.  You should have encountered the T flip-flop in the lesson on flip-flops.  Here is a simulation of a T flip-flop from that lesson.


        In this simulation, there are two (2) T flip-flops.  One T flip-flop is driven by the clock, but the second T flip-flop is driven by the output of the first one.

        The simulation shows how two T flip-flops can work as a counter to count clock pulses.  The question buried in this is whether that will continue to work for larger structures with T flip-flops.  Here's a simulation where you can check that.

        In this simulation, there are four (4) T flip-flops.  One T flip-flop is driven by the clock, but the inputs to all of the other T flip-flops are just outputs from the preceding T flip-flop.  Check the circuit by clicking the clock button (a lot of times!).

        Use this version in which the clock runs continuously (one complete pulse each second).


Q1   In the four bit counter above, does it count UP or DOWN?

Q2   In the four bit counter above, look at the inverted outputs (coming out of the inverters above the flip-flops).  Do they seem to count UP or DOWN?

        Now, there's something interesting in all this.  Not only have we built a counter, but we have a counter that can be thought of as counting up or counting down.  Consider the following.         In the simulation above, it might be better to rearrange things to emphasize that this is a counter.  Humans often react better for particular arrangements.  In the simulation below, the LSB is at the bottom, and the MSB is at the top.  Click here to get the simulator in a separate window.

        Counters are very useful devices.  However, you need to know how to use a real-life counter - like a 74193, for example.  You'll find that in the next section.  Then, you can wire up a real-life circuit like the one above.

Using Counters - The 74193

        There are many different integrated circuit counters.  One popular chip is the 74193, which may also be the 74LS193, etc.  The 74193 has the following characteristics.

        Here's the pinout for the 74193 counter.

 There are several items to note on this chip.

        Those other pins can present problems. That's it for this section.  You have what you need to wire up a 74193 chip, and all you need is the chip and a connector board.  Go to it.

Problem and Labs
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