![]() RS232 specifies a number of out of band control signals as well, which were highly useful when devices of varying capabilities, often with limited memory, processing power, or other resources, needed to reliably interoperate with flow control and the need to avoid dropped characters.Īs it turns out, there were nine signals specified within the DB9 serial standard, including a ground. Of course people can adapt an RS-232 connector to include a power connection, but then it doesn't fully meet the RS-232 specification. In fact there is no power pin in the RS-232 specification. ![]() We only use 4 wires (pwr, common, and two data) (Figure above also courtesy of Dallas Semiconductor Application Note 83, Fundamentals of RS–232 Serial Communications) See the Wikipedia article on the D-subminiature connectors for more details.) The 2nd letter is the size of the connector shell, and this smaller connector is size "E", whereas the larger 25-pin connector is size "B" other sizes exist too. The first letter, D, refers to the D-shaped connector's metal shell. (Strictly, it's a D E-9 connector, not a D B-9. All 9 pins have a defined function, whether you use that function or not. It's a similar explanation for the 9-pin connector made popular by its use on the original IBM PC/AT (the earlier PC and PC/XT used the full 25-pin RS-232 connector). Why do we use a DB9 connector for serial com? (Figure above courtesy of Dallas Semiconductor Application Note 83, Fundamentals of RS–232 Serial Communications) This diagram is a brief overview of the pinout of the 25-pin connector: There are lots of features of RS-232 which are little used these days! Use this link to reference the DE9, or DB9 connector pinout and diagram commonly used for serial ports (RS-232).įind the NorComp d-sub panel cut-out, or DB9 connector footprint here.Assuming you mean the standard 25-pin connector, then there is a simple answer: The RS-232 specification states the defined function for every one of the 25 pins bar three. To find out more detailed information, click on a series number above to acces the DB9 connector datasheet & drawing for each type of connector. It is recommended to use machined contacts for more demanding applications that require a more reliable transfer of signal or in systems where a higher number of mating cycles is anticipated. The male version of the DB9 connector contains pins or contacts that are either machined or stamped & formed. ![]() ![]() Over time the terms DB-9 and DE-9 have become synonymous and while technically incorrect as the 9 pin shell size is E, are now considered to be interchangeable terms used industry wide. The next letter is determined by the 5 shell sizes in accordance with pins (A, B, C, D, & E), which is then followed by the number of sockets or pins (9) housed within the connector shell. The prefix “D” represents the d-shaped connector shell of the d-subminiature connector. The DB9 connector, or more accurately the DE9 Connector, is an abbreviated version to reference the 9 pin d-sub connector. Contact us directly if your unique application requires a custom or semi-custom DB9 connector or DB9 cable assembly not currently offered in our standard product offering above. NorComp DB9 connectors are engineered with machined contacts for heavy-duty industry applications or stamped & formed contacts for applications requiring less mating cycles.
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