|The PX74HC138 is a high-speed CMOS device and is pin compatible with low power Schottky TTL (LSTTL).
The PX74HC138 has three data input ports (A0, A1, A2) and eight output ports of low effective decoding (.
The PX74HC138 also has three enable ports (、、E3). If and are LOW and E3 is HIGH, the eight decoding ports output normally, else the eight decoding ports are HIGH.
The PX74HC138 is used in the 3-8 decoding of a multiplexed signal. 3-address data input and 8 data output. The three bit binary weighted address on pins A(0..2) will produce one active low output with the other seven being high. The multiple enable lines allow for the parallel expansion of decoders to achieve 4-16 lines with no external parts and 5-32 lines with a single inverter.
PX74HC138 3-8 Decoder