HD74HC192/HD74HC193
Synchronous Up/Down Decade Counter (Dual Clock Line)
Synchronous Up/Donw 4-bit Binary Counter (Dual Clock Line)
Description
The HD74HC192 is a decade counter, and the HD74HC193 is a binary counter. Both counters have two
separate clock inputs, an up count input and a down count input. All outputs of the flip-flops are
simultaneously triggered on the low to high transition of either clock while the other input is held high.
The direction of counting is determined by which input is clocked.
These counters may be preset by entering the desired data on the data A, data B, data C, and data D inputs.
When the load input is taken low the data is loaded independently of either clock input. This feature allows
the counters to be used as divide-by-n counters by modifying the count length with the preset inputs.
In addition both counters can also be cleared. This is accomplished by inputting a high on the clear input.
All 4 internal stages are set to a low level independently of either count input.
Both a borrow and carry output are provided to enable cascading of both up and down counting functions.
The borrow output produces a negative going pulse when the counter underflows and the carry outputs a
pulse when the counter overflows. The counters can be cascaded by connecting the carry and borrow
outputs of one device to the count up and count down inputs, respectively, of the next device.
Features
High Speed Operation: t
pd
(Clock Up or Count Down to Q) = 21 ns typ (C
L
= 50 pF)
High Output Current: Fanout of 10 LSTTL Loads
Wide Operating Voltage: V
CC
= 2 to 6 V
Low Input Current: 1 A max
Low Quiescent Supply Current: I
CC
(static) = 4 A max (Ta = 25C)
HD74HC192/HD74HC193
5
Timing Chart
HD74HC192
Illustrated below is the following sequence:
1. Clear outputs to zero.
2. Load (preset) to binary seven.
3. Count up to eight, nine, zero, one and two.
4. Count down to one, zero, borrow, nine, eight and seven.
Clear
Load
Carry
Borrow
0
Clear
7
8
9
0
1
2
1
0
9
8
7
Sequence
Illustrated
Count Up
Count Down
Q
A
A
Data
Inputs
B
C
D
Q
B
Q
C
Q
D
Preset
Count Up
Count Down
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