SN54ALS160B THRU SN54ALS163B, SN54AS160 THRU SN54AS163
SN74ALS160B THRU SN74ALS163B, SN74AS160 THRU SN74AS163
SYNCHRONOUS 4-BIT DECADE AND BINARY COUNTERS
SDAS024A – D2661, APRIL 1982 – REVISED MAY 1986
SN54ALS’, SN54AS’ . . . J PACKAGE
SN74ALS’, SN74AS’ . . . D OR N PACKAGE
• Internal Look-Ahead for Fast Counting
• Carry Output for n-Bit Cascading
• Synchronous Counting
(TOP VIEW)
• Synchronously Programmable
V
RCO
Q
Q
B
Q
Q
D
ENT
LOAD
CLR
CLK
A
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
CC
• Package Options include Plastic Small
Outline Packages, Ceramic Chip Carriers,
and Standard Plastic and Ceramic 300-mil
DIPs
A
B
C
D
C
• Dependable Texas Instruments Quality and
ENP
GND
Reliability
description
SN54ALS’, SN54AS’ . . . FK PACKAGE
(TOP VIEW)
These synchronous, presettable counters feature
an internal carry look-ahead for application in
high-speed counting designs. The ’ALS160B,
’ALS162B, ’AS160, and ’AS162 are decade
counters, and the ’ALS161B, ’ALS163B, ’AS161,
and ’AS163 are 4-bit binary counters. Synchro-
nous operation is provided by having all flip-flops
clocked simultaneously so that the outputs
change coincident with each other when so
instructed by the count-enable inputs and internal
gating. This mode of operation eliminates the
output counting spikes that are normally asso-
ciated with asynchronous (ripple clock)
counters. A buffered clock input triggers the four
flip-flops on the rising (positive-going) edge of the
clock input waveform.
3
2
1
20 19
18
Q
Q
A
B
4
5
6
7
8
A
B
17
16
15
14
NC
NC
C
Q
C
Q
D
D
9 10 11 12 13
NC–No internal connection
These counters are fully programmable; that is, they may be preset to any number between 0 and 9, or 15. As
presetting is synchronous, setting up a low level at the load input disables the counter and causes the outputs
to agree with the setup data after the next clock pulse regardless of the levels of the enable inputs.
Theclearfunctionforthe’ALS160B, ’ALS161B, ’AS160, and’AS161isasynchronousandalowlevelattheclear
input sets all four of the flip-flop outputs low regardless of the levels of the clock, load, or enable inputs. This
synchronous clear allows the count length to be modified easily by decoding the Q outputs for the maximum
count desired. The active-low output of the gate used for decoding is connected to the clear input to
synchronously clear the counter to 0000 (LLLL).
The carry look-ahead circuitry provides for cascading counters for n-bit synchronous applications without
additional gating. Instrumental in accomplishing this function are two count-enable inputs and a ripple carry
output. Both count-enable inputs (ENP and ENT) must be high to count, and ENT is fed forward to enable the
ripple carry output. The ripple carry output (RCO) thus enabled will produce a high-level pulse while the count
is maximum (9 or 15 with Q high). This high-level overflow ripple carry pulse can be used to enable successive
A
cascaded stages. Transitions at the ENP or ENT are allowed regardless of the level of the clock input.
These counters feature a fully independent clock circuit. Changes at control inputs (ENP, ENT, or LOAD) that
will modify the operating mode have no effect on the contents of the counter until clocking occurs. The function
of the counter (whether enabled, disabled, loading, or counting) will be dictated solely by the conditions meeting
the stable setup and hold times.
The SN54ALS160B through SN54ALS163B and SN54AS160 through SN54AS163 are characterized for
operation over the full military temperature range of –55°C to 125°C. The SN74ALS160B through
SN74ALS163B and SN74AS160 through SN74AS163 are characterized for operation from 0°C to 70°C.
Copyright 1986, Texas Instruments Incorporated
5BASIC
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
1
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