BCD DECADE COUNTERS/
4-BIT BINARY COUNTERS
The LS160A / 161A / 162A / 163A are high-speed 4-bit synchronous count-
ers. They are edge-triggered, synchronously presettable, and cascadable
MSI building blocks for counting, memory addressing, frequency division and
other applications. The LS160A and LS162A count modulo 10 (BCD). The
LS161A and LS163A count modulo 16 (binary.)
The LS160A and LS161A have an asynchronous Master Reset (Clear)
input that overrides, and is independent of, the clock and all other control
inputs. The LS162A and LS163A have a Synchronous Reset (Clear) input that
overrides all other control inputs, but is active only during the rising clock
edge.
BCD (Modulo 10)
Asynchronous Reset
Synchronous Reset
LS160A
LS162A
Binary (Modulo 16)
LS161A
LS163A
SN54/74LS160A
SN54/74LS161A
SN54/74LS162A
SN54/74LS163A
BCD DECADE COUNTERS/
4-BIT BINARY COUNTERS
LOW POWER SCHOTTKY
J SUFFIX
CERAMIC
CASE 620-09
16
1
•
•
•
•
•
•
Synchronous Counting and Loading
Two Count Enable Inputs for High Speed Synchronous Expansion
Terminal Count Fully Decoded
Edge-Triggered Operation
Typical Count Rate of 35 MHz
ESD > 3500 Volts
CONNECTION DIAGRAM DIP
(TOP VIEW)
VCC
16
TC
15
Q0
14
Q1
13
Q2
12
Q3
11
CET
10
PE
9
16
1
N SUFFIX
PLASTIC
CASE 648-08
NOTE:
The Flatpak version
has the same pinouts
(Connection Diagram) as
the Dual In-Line Package.
*MR for LS160A and LS161A
*SR for LS162A and LS163A
1
*R
2
CP
3
P0
4
P1
5
P2
6
P3
7
CEP
8
GND
16
1
D SUFFIX
SOIC
CASE 751B-03
ORDERING INFORMATION
SN54LSXXXJ
SN74LSXXXN
SN74LSXXXD
Ceramic
Plastic
SOIC
PIN NAMES
PE
P0 – P3
CEP
CET
CP
MR
SR
Q0 – Q3
TC
Parallel Enable (Active LOW) Input
Parallel Inputs
Count Enable Parallel Input
Count Enable Trickle Input
Clock (Active HIGH Going Edge) Input
Master Reset (Active LOW) Input
Synchronous Reset (Active LOW) Input
Parallel Outputs (Note b)
Terminal Count Output (Note b)
LOADING
(Note a)
HIGH
1.0 U.L.
0.5 U.L.
0.5 U.L.
1.0 U.L.
0.5 U.L.
0.5 U.L.
1.0 U.L.
10 U.L.
10 U.L.
LOW
0.5 U.L.
0.25 U.L.
0.25 U.L.
0.5 U.L.
0.25 U.L.
0.25 U.L.
0.5 U.L.
5 (2.5) U.L.
5 (2.5) U.L.
LOGIC SYMBOL
9
3
4
5
6
PE
7
10
2
CEP
CET
CP
*R
P0
P1
P2
P3
TC
15
Q0 Q1
Q2 Q3
NOTES:
a) 1 TTL Unit Load (U.L.) = 40
µA
HIGH/1.6 mA LOW.
b) The Output LOW drive factor is 2.5 U.L. for Military (54) and 5 U.L. for Commercial (74)
Temperature Ranges.
1
14
13
12
11
VCC = PIN 16
GND = PIN 8
*MR for LS160A and LS161A
*SR for LS162A and LS163A
FAST AND LS TTL DATA
5-278
SN54/74LS160A
•
SN54/74LS161A
SN54/74LS162A
•
SN54/74LS163A
STATE DIAGRAM
LS160A
•
LS162A
0
1
2
3
4
0
LS161A
•
LS163A
1
2
3
4
LOGIC EQUATIONS
Count Enable = CEP
•
CET
•
PE
TC for LS160A & LS162A = CET
•
Q0
•
Q1
•
Q2
•
Q3
TC for LS161A & LS163A = CET
•
Q0
•
Q1
•
Q2
•
Q3
Preset = PE
•
CP + (rising clock edge)
Reset = MR (LS160A & LS161A)
Reset = SR
•
CP + (rising clock edge)
Reset =
(LS162A & LS163A)
15
5
15
5
14
6
14
6
13
7
13
7
12
11
10
9
8
12
11
10
9
8
NOTE:
The LS160A and LS162A can be preset to any state,
but will not count beyond 9. If preset to state 10, 11,
12, 13, 14, or 15, it will return to its normal sequence
within two clock pulses.
FUNCTIONAL DESCRIPTION
The LS160A / 161A / 162A / 163A are 4-bit synchronous
counters with a synchronous Parallel Enable (Load) feature.
The counters consist of four edge-triggered D flip-flops with
the appropriate data routing networks feeding the D inputs. All
changes of the Q outputs (except due to the asynchronous
Master Reset in the LS160A and LS161A) occur as a result of,
and synchronous with, the LOW to HIGH transition of the
Clock input (CP). As long as the set-up time requirements are
met, there are no special timing or activity constraints on any
of the mode control or data inputs.
Three control inputs — Parallel Enable (PE), Count Enable
Parallel (CEP) and Count Enable Trickle (CET) — select the
mode of operation as shown in the tables below. The Count
Mode is enabled when the CEP, CET, and PE inputs are HIGH.
When the PE is LOW, the counters will synchronously load the
data from the parallel inputs into the flip-flops on the LOW to
HIGH transition of the clock. Either the CEP or CET can be
used to inhibit the count sequence. With the PE held HIGH, a
LOW on either the CEP or CET inputs at least one set-up time
prior to the LOW to HIGH clock transition will cause the
existing output states to be retained. The AND feature of the
two Count Enable inputs (CET
•
CEP) allows synchronous
cascading without external gating and without delay accu-
mulation over any practical number of bits or digits.
The Terminal Count (TC) output is HIGH when the Count
Enable Trickle (CET) input is HIGH while the counter is in its
maximum count state (HLLH for the BCD counters, HHHH for
the Binary counters). Note that TC is fully decoded and will,
therefore, be HIGH only for one count state.
The LS160A and LS162A count modulo 10 following a
binary coded decimal (BCD) sequence. They generate a TC
output when the CET input is HIGH while the counter is in state
9 (HLLH). From this state they increment to state 0 (LLLL). If
loaded with a code in excess of 9 they return to their legitimate
sequence within two counts, as explained in the state
diagram. States 10 through 15 do
not
generate a TC output.
The LS161A and LS163A count modulo 16 following a
binary sequence. They generate a TC when the CET input is
HIGH while the counter is in state 15 (HHHH). From this state
they increment to state 0 (LLLL).
The Master Reset (MR) of the LS160A and LS161A is
asynchronous. When the MR is LOW, it overrides all other
input conditions and sets the outputs LOW. The MR pin should
never be left open. If not used, the MR pin should be tied
through a resistor to VCC, or to a gate output which is
permanently set to a HIGH logic level.
The active LOW Synchronous Reset (SR) input of the
LS162A and LS163A acts as an edge-triggered control input,
overriding CET, CEP and PE, and resetting the four counter
flip-flops on the LOW to HIGH transition of the clock. This
simplifies the design from race-free logic controlled reset
circuits, e.g., to reset the counter synchronously after
reaching a predetermined value.
MODE SELECT TABLE
*SR
L
H
H
H
H
PE
X
L
H
H
H
CET
X
X
H
L
X
CEP
X
X
H
X
L
Action on the Rising Clock Edge (
RESET (Clear)
LOAD (Pn
Qn)
COUNT (Increment)
NO CHANGE (Hold)
NO CHANGE (Hold)
)
*For the LS162A and
*LS163A
only.
H = HIGH Voltage Level
L = LOW Voltage Level
X = Don’t Care
FAST AND LS TTL DATA
5-279
SN54/74LS160A
•
SN54/74LS161A
SN54/74LS162A
•
SN54/74LS163A
AC SETUP REQUIREMENTS
(TA = 25°C)
Limits
Symbol
tWCP
tW
ts
ts
th
th
trec
*CEP, CET or DATA
Parameter
Clock Pulse Width Low
MR or SR Pulse Width
Setup Time, other*
Setup Time PE or SR
Hold Time, data
Hold Time, other
Recovery Time MR to CP
Min
25
20
20
25
3
0
15
Typ
Max
Unit
ns
ns
ns
ns
ns
ns
ns
Test Conditions
VCC = 5.0 V
DEFINITION OF TERMS
SETUP TIME (ts) — is defined as the minimum time required
for the correct logic level to be present at the logic input prior to
the clock transition from LOW to HIGH in order to be recog-
nized and transferred to the outputs.
HOLD TIME (th) — is defined as the minimum time following
the clock transition from LOW to HIGH that the logic level must
be maintained at the input in order to ensure continued recog-
nition. A negative HOLD TIME indicates that the correct logic
level may be released prior to the clock transition from LOW to
HIGH and still be recognized.
RECOVERY TIME (trec) — is defined as the minimum time re-
quired between the end of the reset pulse and the clock transi-
tion from LOW to HIGH in order to recognize and transfer
HIGH Data to the Q outputs.
AC WAVEFORMS
tW(H)
1.3 V
tW(L)
1.3 V
tPLH
1.3 V
OTHER CONDITIONS:
PE = MR (SR) = H
tW
MR
1.3 V
trec
1.3 V
CP
tPHL
OTHER CONDITIONS:
PE = L
P0 = P1 = P2 = P3 = H
CP
tPHL
Q
1.3 V
CEP = CET = H
Q0
⋅
Q1
⋅
Q2
⋅
Q3
1.3 V
Figure 1. Clock to Output Delays, Count
Frequency, and Clock Pulse Width
Figure 2. Master Reset to Output Delay, Master Reset
Pulse Width, and Master Reset Recovery Time
FAST AND LS TTL DATA
5-282
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