The following links are to pages useful to some engineers who design serial circuits. The information and products contained on the links may or may not be useful or correct for your application.
L-Com
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C2G (Cables to Go)
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9M/M adapter at Mouser
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9M/F Phoneix Connector adapter at Mouser
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Office Depot, null modem cable
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Jumper box, 25 pin
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Pinout for RS-232 on DB9
While all 9 pins are listed, most applications only use 3 or 5 of these.
| Function Name | Data Terminal Equipment Upstream CPU, PLCin/Out |
Pin # | Data Circuit Terminating EquipmentDownstreamModems, Peripherals, Dogcatcher Data Logger in/Out |
|---|---|---|---|
| dcd | In | 1 | Out |
| RxD | In | 2 | Out |
| TxD | Out | 3 | In |
| DTR | Out | 4 | In |
| Ground | – | 5 | – |
| DSR | In | 6 | Out |
| RTS | Out | 7 | In |
| CTS | In | 8 | Out |
| RI | In | 9 | Out |
Here’s a good set of figures for D-sub 9 male and female connectors, as viewed from the pin side (not the cable side).
RS-232 Standard
While many companies have taken liberties, an official RS-232 standard does exist. The Telecommunications Industry Association sells it for $147.
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