Unit LoadingFan Out

54F74F

Pin Names

Description

UL

HIGHLOW

Carry Input

1020

Carry Generate Inputs (Active LOW)

10140

Carry Generate Input (Active LOW)

10160

Carry Generate Input (Active LOW)

1080

Carry Propagate Inputs (Active LOW)

1080

Carry Propagate Input (Active LOW)

1060

Carry Propagate Input (Active LOW)

1040

Carry Outputs

50333

b

1 mA20 mA

G

Carry Generate Output (Active LOW)

50333

b

1 mA20 mA

P

Carry Propagate Output (Active LOW)

50333

b

1 mA20 mA

Functional Description

The ’F182 carry lookahead generator accepts up to four

’F182 also has Active LOW Carry Propagate (P) and Carry

Generate (G) outputs which may be used for further levels

of lookahead The logic equations provided at the outputs

are

G

e

P

e

Also the ’F182 can be used with binary ALUs in an active

LOW or active HIGH input operand mode The connections

(Figure 1) to and from the ALU to the carry lookahead gen-

erator are identical in both cases Carries are rippled be-

tween lookahead blocks The critical speed path follows the

circled numbers There are several possible arrangements

for the carry interconnects but all achieve about the same

speed A 28-bit ALU is formed by dropping the last ’F181 or

’F381

TLF9492 – 5

FIGURE 1 32-Bit ALU with Rippled Carry between 16-Bit Lookahead ALUs

ALUs may be either ’F181 or ’F381

2