digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usual ...

, an address decoder is a

binary decoder In digital electronics, a binary decoder is a combinational logic circuit that converts binary information from the n coded inputs to a maximum of 2n unique outputs. They are used in a wide variety of applications, including instruction decoding, ...

that has two or more inputs for

address An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along w ...

bits and one or more outputs for device selection signals. When the address for a particular device appears on the address inputs, the decoder asserts the selection output for that device. A dedicated, single-output address decoder may be incorporated into each device on an address bus, or a single address decoder may serve multiple devices. A single address decoder with n address input bits can serve up to 2ⁿ devices. Several members of the

7400 series The 7400 series of integrated circuits (ICs) are a popular logic family of transistor–transistor logic (TTL) logic chips. In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-co ...

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

s can be used as address decoders. For example, when used as an address decoder, the 74154Datasheet for 74HCT154
/ref> provides four address inputs and sixteen (i.e., 2⁴) device selector outputs. An address decoder is a particular use of a

circuit known as a "

demultiplexer In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The sel ...

" or "demux" (the 74154 is commonly called a "4-to-16 demultiplexer"), which has many other uses besides address decoding. Address decoders are fundamental building blocks for systems that use

buses A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

. They are represented in all integrated circuit families and processes and in all standard

FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...

and

ASIC An application-specific integrated circuit (ASIC ) is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficien ...

libraries. They are discussed in introductory textbooks in digital logic design.

Address decoder selects the storage cell in a memory

An address decoder is a commonly used component in microelectronics that is used to select memory cells in randomly addressable memory devices. Such a memory cell consists of a fixed number of memory elements or bits. The address decoder is connected to an address bus and reads the address created there. Using a special switching logic, it uses this address to calculate which memory cell is to be accessed. It then selects that cell by selecting it via a special control line. This line is also known as the select line. In dynamic memories (DRAM), there are row and column select lines on the memory matrix, which are controlled by address decoders integrated in the chip. Depending on the type of decoder, the logic used to select the memory cell can under certain circumstances be programmable.

Address decoder selects the appropriate memory module

An address decoder is also used to select the appropriate one of multiple memory modules or memory chips when a particular address is provided by the processor system's address bus. For this purpose, the memory modules or memory chips have selection inputs, usually referred to as chip select pin (CS) or chip enable pin (CE) pin. These inputs often have a negative logic function ( or ), i. H. with an adjacent logical zero (voltage level low) is selected. The address decoder uses the different combinatorial logic to place the memory modules or chips in the address space of a processor. The memory modules often have a smaller capacity than the address space. In most cases, several modules can be used, even if they are completely identical in structure. It must be ensured that they differ in the address range.

References

Digital circuits {{Compu-hardware-stub