HD74HC182 Datasheet, PDF(1/9 Page) Hitachi Semiconductor

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HD74HC182 Datasheet, PDF (1/9 Pages) Hitachi Semiconductor – Look-Ahead Carry Generator

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 (Cn+x, Cn+y, Cn+z) across four groups of binary adders. The

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:

Cn+x = Y0 (X0 + Cn)

Cn+y = Y1 {X1 + Y0 (X0 + Cn)}

Cn+z = Y2 [X2 + Y1 {X1 + Y0 (X0 + Cn)}]

Y = Y3 (X3 + Y2) (X3 + X2 + Y1) (X3 + X2 + X1 + Y0)

X = X3 + X2 + X1 + X0

Cn+x = G0 + P0Cn

Cn+y = G1 + P1G0 + P1P0Cn

Cn+z = G2 + P2G1 + P2P1G0 + P2P1P0Cn

G = G3 + P3G2 + P3P2G1 + P3P2P1G0

P = P3P2P1P0

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.

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