| Counters |
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.
- The 74193 is an Up-Down
counter. It can count in both directions, but only one direction at at
time.
- You can preload a count into
the 74193.
- You can reset the 74193.
- There are 16 pins on the
package, and as usual, power is applied to the corners. Pin 16 gets +5v,
and pin 8 is grounded.
Here's the pinout for the 74193 counter.
There are several items to note on this chip.
- The power is applied at the
corners (pins 8 and 16 here) just as in many other logic chips.
- There are four count outputs,
A, B, C and D. These are the bits in the count, and A is the least
significant bit (LSB) and D is the most significant bit (MSB).
- There are two inputs, pins 4
& 5.
- To count up, hold the
down pin, #4, high (5v) and put the pulse in pin #5.
- To count down, hold the
up pin, #5, high (5v) and put the pulse in pin #4.
- There are lots of other pins
but we won't go into that here. You can use the remaining pins to preload a
count into the counter, and there are borrow and carry pins. You use those
pins to connect this chip to other 74193 chips when you need to count more
than 4 bits.
Those other pins can present problems.
- Pin 14 is a clear input.
When you put a 1 on this pin, the counter is cleared, i. e. reset to zero.
- Make this pin zero!
(Connect it to ground.)
- Pin 11 is for a load signal.
When this pin goes high (1), the data inputs are loaded into the counter.
- Make this pin zero!
(Connect it to ground.)
- Pin 12 is a carry output.
Useful for 8, 12 or 16 bit counters, etc., using more than one chip.
- Pin 13 is a borrow output.
Useful when counting down in counters with more than four bits.
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.
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