The 74HC/HCT283 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A.
The 74HC/HCT283 add two 4-bit binary words (An plus Bn) plus the incoming carry. The binary sum appears on the sum outputs (∑1 to ∑4) and the out-going carry (COUT) according to the equation: