Pinout

In electronics, a pinout (sometimes written "pin-out") is a cross-reference between the contacts, or pins, of an electrical connector or electronic component, and their functions. "Pinout" now supersedes the term "basing diagram" that was the standard terminology used by the manufacturers of vacuum tubes and the RMA. The RMA started its standardization in 1934, collecting and correlating tube data for registration at what was to become the EIA. The EIA (Electronic Industries Alliance) now has many sectors reporting to it, and sets what are known as EIA standards where all registered pinouts and registered jacks can be found.

Not to be confused with PinOut.
A pinout diagram of a very common 555 timer integrated circuit showing its 8 pins (numbered 1-8) and their corresponding functions ("ground", "trigger", "output", etc.)

Purpose

The functions of contacts in electrical connectors, be they power- or signaling-related, must be specified in order for connectors to be interchangeable. When connected, each contact of a connector must mate with the contact on the other connector that has the same function. If contacts of disparate functions are allowed to make contact, the connection may fail and damage may result. Therefore, pinouts are a vital reference when building and testing connectors, cables, and adapters.

If one has specified wires within a cable (for instance, the colored Ethernet cable wires in ANSI/TIA-568 T568A), then the order in which different color wires are attached to pins of an electrical connector defines the wiring scheme. In any multi-pin connector, there are multiple ways to map wires to pins, so different configurations may be created which superficially look identical but function differently. These configurations are defined by pinouts. Many connectors have multiple standard pinouts in use for different manufacturers or applications.[1]

Terminology

While one usage of the word pin is to refer to electrical contacts of, specifically, the male gender, its usage in pinout does not imply gender: the contact-to-function cross-reference for a connector that has only female socket contacts is still called a pinout.

Representation

The pinout can typically be shown as a table or diagram, though it is necessary to clarify how to view the diagram, stating if it shows the backside of the connector (where wires are attached) or the "mating face" of the connector. Published pinouts, which are particularly important when different manufacturers want to interconnect their products using open standards, are typically provided by the connector or equipment manufacturer. Some pinouts are provided by 3rd parties since some connectors are not well documented by the manufacturer.

While repairing electronic devices, an electronics technician uses electronic test equipment to "pin out" each component on a PCB. The technician probes each pin of the component in turn, comparing the expected signal on each pin to the actual signal on that pin.

Example pinouts

USB pinout

Viewed from the front (outside) of Female Type A USB receptacle:

  1. +5V (Red)
  2. −Data (White)
  3. +Data (Green)
  4. GND (Black)

PS/2 pinout
PS/2 connector pinout
Pin numberNamePurpose
1DATAData
2Not used
3GNDGround
4Vcc+5V Common-collector voltage
5CLKClock signal
6Not used

4017 decade counter
4017 pinout
Pin numberNamePurpose
16The 6th sequential output
22The 2nd sequential output
31The 1st sequential output
43The 3rd sequential output
57The 7th sequential output
68The 8th sequential output
74The 4th sequential output
80 V, VDDThe connection to the 0 V rail
99The 9th sequential output
105The 5th sequential output
1110The 10th sequential output
12COCarry out output - outputs high on counts 0 to 4, outputs low on counts 5 to 9 (thus a transition from low to high occurs when counting from 9 back to 0)
13ENLatch enable - latches on the current output when high (i.e. the chip counts when EN is low)
14CLKClock in
15RSTReset - sets output 1 high and outputs 2 through 10 low, when taken high
16+9 V, VCCThe connection to the +VCC rail (voltage between +3 V and +15 V)

LM741 operational amplifier

See also

References
  1. "Handbook of hardware schemes, cables layouts and connectors". pinouts.ru. Retrieved 2016-04-25.
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