DESCRIPTION
They are cascadable to perform full look-ahead across nbit adders. Carry, generate-carry, and propagate-carry functions are provided as shown in the pin connection table. When used in conjunction with the HC181 arithmetic logic unit, these generators provide high-speed carry look-ahead capability for any word length. Each HC182 generates the look-ahead (anticipated carry) across a group of four ALU’s and, in addition, other carry lookahead circuits may be employed to anticipate carry across sections of four look-ahead packages up to n-bits. The method of cascading circuits to perform multi-level look-ahead is illustrated under typical application data. Carry input and output of the ALUs are in their true form, and the carry propagate (P) and carry generate (G) are in negated form ; therefore, the carry functions (inputs, outputs, generate, and propagate) of the look-ahead generators are implemented in the compatible forms for direct connection to the ALU. Reinterpretation of carry functions as explained on the HC181 data sheet are also applicable to and compatible with the look-ahead generator.
STMicroelectronics
