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SCAS106A − D3455, FEBRUARY 1990 − REVISED APRIL 1993
DW OR N PACKAGE
(TOP VIEW)
• Inputs Are TTL-Voltage Compatible
• Single Down/Up Count Control Line
• Look-Ahead Circuitry Enhances Speed of
RCO
D/U
CLK
A
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
Cascaded Counters
Q
A
• Fully Synchronous in Count Modes
Q
B
• Asynchronously Presettable With Load
GND
GND
GND
GND
B
V
V
Control
CC
CC
• Flow-Through Architecture Optimizes
C
PCB Layout
Q
Q
D
CTEN
LOAD
C
D
• Center-Pin V
and GND Configurations to
Minimize High-Speed Switching Noise
CC
MAX/MIN
• EPICt (Enhanced-Performance Implanted
CMOS) 1-mm Process
• Package Options Include Plastic
Small-Outline Packages and Standard
Plastic 300-mil DIPs
description
The 74ACT11191 is a synchronous, 4-bit binary reversible up/down counter. A synchronous counting operation
is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other
when so instructed by the steering logic. This mode of operation eliminates the output counting spikes normally
associated with asynchronous (ripple clock) counters.
The outputs of the four flip-flops are triggered on a low-to-high-level transition of the clock input if the enable
input (CTEN) is low. A high at CTEN inhibits counting. The direction of the count is determined by the level of
the down/up (D/U) input. When D/U is low, the counter counts up and when D/U is high, it counts down.
These counters feature a fully independent clock circuit. Changes at the control inputs (CTEN and D/U) that
will modify the operating mode have no effect on the contents of the counter until clocking occurs. The function
of the counter will be dictated solely by the condition meeting the stable setup and hold times.
†
logic symbol
CTRDIV16
12
20
G1
CTEN
D/U
10
1
M2 [DOWN]
M3 [UP]
1,2−/1,3+
G4
2(CT=0)Z6
3(CT=15)Z6
MAX/MIN
RCO
19
11
CLK
6,1,4
LOAD
C5
2
3
8
9
18
17
14
13
A
B
5D
[1]
[2]
[4]
[8]
Q
Q
Q
Q
A
B
C
D
C
D
†
This symbol is in accordance with ANSI/IEEE Std 91-1984
and IEC Publication 617-12.
EPIC is a trademark of Texas Instruments Incorporated.
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Copyright 1993, Texas Instruments Incorporated
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2−1
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