address decoder

In digital electronics, an Address decoder is a circuit that has two or more bits of an address bus as inputs and that has one or more device selection lines as outputs. When the address for a particular device appears on the address bus, the address decoder asserts the selection line for that device. A separate single-device address decoder may be incorporated into each device on an address bus, or a single address decoder may serve multiple devices. In the latter case, an address decoder with N address input bits can serve up to 2N separate devices. Several members of the 7400 series of integrated circuit are address decoders. An example is the 74154 . This address decoder has four address inputs and sixteen (i.e., 24 ) device selector outputs. An address decoder is also referred to as a "demultiplexer" or "demux," although these terms are more general and can refer to devices other than address decoders. The 74154 mentioned above can be called a "4-to-16 demux."
See more at Wikipedia.org...