M74HC181 Просмотр технического описания (PDF) - STMicroelectronics
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M74HC181 Datasheet PDF : 15 Pages
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M74HC181
DESCRIPTION (Continued)
B inputs , it will assume a high level to indicated
equality (A=B). The ALU should be in the subtract
mode with Cn = H when performing this
comparison. The A = B output is open drain so
that it can be wire-AND connected to give a
comparison for more that four bits. The carry
output (Cn + 4) can also be used to supply relative
magnitude information.
Again, the ALU should be placed in the subtract
mode by placing the function select inputs S3, S2,
S1, S0 at L, H, H, L, respectively. These circuits
have been designed to not only incorporate all of
the designer’s requirements for arithmetic
operations, but also to provide 16 possible
function of two Boolean variables without the use
of external circuitry. These logic functions are
selected by use of the four function-select inputs
(S0, S1, S2, S3) with the mode - control (M) at a
high level to disable the internal carry.
All inputs are equipped with protection circuits
against static discharge and transient excess
voltage.
INPUT AND OUTPUT EQUIVALENT CIRCUITS
ONLY OUTPUT A = B
PIN DESCRIPTION
PIN No
2, 23, 21, 19
1, 22, 20, 18
6, 5, 4, 3
7
8
9, 10, 11, 13
14
15
16
17
12
24
SYMBOL
A0 to A3
B0 to B3
S0 to S3
Cn
M
F0 to F3
A=B
P
Cn + 4
G
GND
VCC
NAME AND FUNCTION
Word A Inputs
Word B Inputs
Function Select Inputs
Inv. Carry Input
Mode Control Input
Function Outputs
Comparator Output
Carry Propagate Output
Inv. Carry Output
Carry Generate Output
Ground (0V)
Positive Supply Voltage
PIN NUMBER
ACTIVE LOW DATA (Table 1)
ACTIVE HIGH DATA (Table 1)
2 1 23 22 21 20 19 18 9 10 11 13 7 16 15 17
A0 B0 A1 B1 A2 B2 A3 B3 F0 F1 F2 F3 Cn Cn + 4 P G
A0 B0 A1 B1 A2 B2 A3 B3 F0 F1 F2 F3 Cn Cn + 4 X Y
INPUT CN
H
H
L
L
INPUT CN + 4
H
L
H
L
ACTIVE LOW DATA (FIGURE1)
A>B
A<B
A>B
A<B
ACTIVE HIGH DATA (FIGURE 2)
A<B
A>B
A<B
A>B
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