Working of 74HC138 IC
74HC138 is a decoder of the type octal 3- to- 8 Line Decoder / Demulator and Inverter.
The chip enables 3 pins - A, B and C - to output 8-bit , meaning that decodes three address lines in 8 possible ways . Simple, with 3 input bits to form 8 Address : 2 3 = 8; See the truth table:
An address decoder is also called a " demultiplexer " or " demux " . Although these terms are more generic and can refer to devices other than decoders addresses, TTL 74138 mentioned here can be called " demux 3- to -8" .
Decoders addresses are fundamental building blocks for systems using bus bars. They are represented in all families of integrated circuits and all the standard libraries FPGA and ASIC . They are discussed in introductory texts in digital logic design
