CD40181BMS

CD40181BMS December 1992 CMOS 4 Bit Arithmetic Logic Unit Description The CD40181BMS is a low power four bit parallel arithmetic logic unit (ALU) capable of providing 16 binary arithmetic operations on two four-bit words and 16 logical functions of two Boolean variables. The mode control input M selects logical (M = High) or arithmetic (M = Low) operation. The four select inputs (S0, S1, S2, and S3) select the desired logical or arithmetic functions, which include AND, OR, NAND, NOR and exclusive-OR and-NOR in the logic mode, and addition, subtraction, decrement, left-shift and straight transfer in the arithmetic mode, according to the truth table. The CD40181BMS operation may be interpreted with either active-low or active-high data at the A and B word inputs and the function outputs F, by using the appropriate truth table. The CD40181BMS contains logic for full look ahead carry operation for fast carry generation using the carry-generate and carry-propagate outputs G and P for the four bits of the CD40181BMS. Use of the CD40182BMS look-ahead carry generator in conjunction with multiple CD40181BMS’s permits high speed arithmetic operations on long words. A ripple carry output Cn+4 is available for use in systems where speed is not of primary importance. Also included in the CD40181BMS is a comparator output A = B, which assumes a high level whenever the two four-bit input words A and B are equal and the device is in the subtract mode. In addition, relative magnitude informa...