74HC/HCT158

Features:

· Inverting data path
· Output capability: standard
· ICC category: MSI



Pinout




Description

   The 74HC/HCT158 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/HCT158 are quad 2-input multiplexers which select 4 bits of data from two sources and are controlled by a common data select input (S). The four outputs present the selected data in the inverted form. The enable input (E ) is active LOW.

   When E of the 74HC/HCT158 is HIGH, all the outputs (1Y to 4Y ) are forced HIGH 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 "158". The state of S determines the particular register from which the data comes. It can also be used as a function generator.

   The 74HC/HCT158 is useful for implementing highly irregular logic by generating any four of the 16 different functions of two variables with one variable common.

   The "158" is the logic implementation of a 4-pole, 2-position switch, where the position of the switch is determined by the logic levels applied to S.

   The logic equations for the output of the 74HC/HCT158 are:

   1Y = E .(1l1.S + 1l0.S )

   2Y = E .(2l1.S + 2l0.S )

   3Y = E .(3l1.S + 3l0.S )

   4Y = E .(4l1.S + 4l0.S )

   The "158" is identical to the "157" but has inverting outputs.