SN74LS181N

The SN74LS181N is an arithmetic Logic Unit or Function Generator that have a complexity of 75 equivalent gates on a monolithic chip. These circuits perform 16 binary arithmetic operations on two 4-bit words as shown in Tables 1 and 2. These operations are selected by the four function-select lines (S0, S1, S2, S3) and include addition, subtraction, decrement and straight transfer. When performing arithmetic manipulations, the internal carries must be enabled by applying a low-level voltage to the mode control input (M). This circuit have been designed to not only incorporate all of the designer's requirements for arithmetic operations, but also to provide 16 possible functions of two Boolean variables without the use of external circuitry. This logic function is selected by use of the 4-function-select inputs (S0, S1, S2, S3) with the mode-control input (M) at a high level to disable the internal carry.