HIT HD74HC182 Datasheet
HD74HC182
Look-Ahead Carry Generator
Description
The HD74HC182 is a high-speed Carry Lockahead Generator. It is used with the HD74HC181 4-Bit
Arithmetic Logic Unit to provide high-speed lockahead over World lengths of more than four bits. The
device accepts up to four pairs of active-low Carry Propagate (P0, P1, P2, P3) and Carry Generate (G0, G1,
G2, G3) signals and an active-high carries (C
HD74HC182 also has active-low Carry Propagate (P) and Carry Generate (G) outputs which may be used
for further levels of lockahead.
The logic equations provided at the outputs are:
n+x
, C
n+y, Cn+z
) across four groups of binary adders. The
C
= Y0 (X0 + Cn)
n+x
C
= Y1 {X1 + Y0 (X0 + Cn)}
n+y
C
= Y2 [X2 + Y1 {X1 + Y0 (X0 + Cn)}]
n+z
Y = Y3 (X3 + Y2) (X3 + X2 + Y1) (X3 + X2 + X1 + Y0)
X = X3 + X2 + X1 + X
0
or
C
= G0 + P0C
n+x
C
= G1 + P1G0 + P1P0C
n+y
C
= G2 + P2G1 + P2P1G0 + P2P1P0C
n+z
G = G3 + P3G2 + P3P2G1 + P3P2P1G
P = P3P2P1P
n
n
n
0
0
Also, the HD74HC182 can be used with binary ALUs in an active-low or active-high input operand mode.
The connections to and from the ALU to the carry lookahead generator are identical in both cases.
HD74HC182
Features
• High Speed Operation: tpd (Pn to P) = 11 ns typ (CL = 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: VCC = 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
Pin Designations
Item Pin No. Functions
, G1, G2, G
G
0
P0, P1, P2, P
C
n
C
, C
n+x
n+y
, C
3
3
n+z
G 10 Active-low carry propagate output
P 7 Active-low carry propagate output
V
CC
GND 8 Ground
3, 1, 14, 5 Active-low carry generate inputs
4, 2, 15, 6 Active-low carry propagate inputs
13 Carry input
12, 11, 9 Carry outputs
16 Supply voltage
2
Pin Arrangement
HD74HC182
Logic Diagram
Inputs
Output
G1
P1
C0
P0
G3
P3
GND
1
2
3
4
5
6
7
P
P1
G
P0
G3
P3
P
0
G1
Cn+z
P2
G
Cn
Cn+x
Cn+y
2
G
8
16
15
14
13
12
11
10
V
CC
P2
G2
Inputs
Cn
Cn+x
Cn+y
Outputs
G
9
C
n+z
(Top view)
P
P
G3
P2
G2
P1
G1
P0
G0
Cn
G
3
n+z
C
Cn+y
Cn+x
3
Loading...