1. 74LS283 4-Bit Binary Adder with Fast Carry
Heather Weaver

2. Pin mappings Pins 12, 14, 3, and 5 are input A (MSB to LSB)
Pins 11, 15, 2, and 6 are input B (MSB to LSB)
Pins 10, 13, 1, and 4 are the outputs (MSB to LSB)
Pin 8 is ground
Pin 15 is Vcc
Pin 7 is carry in and Pin 9 is carry out

3. Schematic

4. Bit Slices Equation for ith bit Si = Ai XOR Bi XOR ci
A and B are the inputs
C is the carry-in bit
Carry occurs 2 ways
Generate – the added bits are both 1
Propagate – one add bit is 1 and the carry in bit is 1

5. Timing of CLA Equations for generate & propagate
Generate: gi = Ai AND Bi
Propagate: pi = Ai OR Bi
Carry-out in terms of generate and propagate: ci+1 = gi AND pi OR ci
Each bit slice of CLA has 3 levels of delay
One level for generate & propagate signals
Two levels for sum of products