NXP 74HC157N 芯片, 74HC CMOS逻辑器件
The is a 2-input Quad Multiplexer pin compatible with low-power Schottky TTL. It selects 4-bit of data from two sources under the control of a common data select input S. The enable input E is active LOW. When E is HIGH, all of the outputs 1Y to 4Y are forced low regardless of all other input conditions. Moving the data from two groups of registers to four common output buses is a common use of the multiplexer. The state of the common data select input S determines the particular register from which the data comes. It can also be used as function generator. The device is useful for implementing highly irregular logic by generating any four of the 16 different functions of two variables with one variable common. It is logic implementation of a 4-pole, 2-position switch, where the position of the switch is determined by the logic levels applied to S.