Serial 9 pin loopback wiring help \ VOGONS

Serial 9 pin loopback wiring help

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First post, by GabrielKnight123

Posted on 2022-01-01, 17:59

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I have a problematic 9 pin serial port COM A on a 486 motherboard so I'm going to make a loopback cable and use AMIDiag but I see there are a few ways to make one from different pin wire connections, in my book it says to connect pins:

1 to 7 to 8
2 to 3
4 to 6 to 9

The above is for a standard IBM type 9 pin serial female DB9S and a web site https://ardent-tool.com/misc/wrap_plugs.html says different and I dont understand the diagram which one do I use?

Reply 1 of 4, by snufkin

Posted on 2022-01-01, 18:26

snufkin Offline

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Are they different? From ardent-tool:

1DCD 1 -----+-- 7 RTS
2           |
3           +-- 8 CTS
4
5RXD 2 -------- 3 TXD
6
7DTR 4 -----+-- 9 RI
8           |
9           +---6 DSR

Which looks like 1 to 7 & 8, 2 to 3 and 4 to 6 & 9, same as your book?

Reply 2 of 4, by BitWrangler

Posted on 2022-01-01, 18:32

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I would assume the IBM one is correct for IBM diagnostics, but other diagnostics have their own ideas...

https://airborn.com.au/serial/rs232.html
https://www.epanorama.net/hwbooks/cable/loopb … ck9checkit.html

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 3 of 4, by TheMobRules

Posted on 2022-01-01, 18:35

TheMobRules Offline

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I use this one with CheckIt.

Reply 4 of 4, by GabrielKnight123

Posted on 2022-01-01, 20:04

GabrielKnight123 Offline

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Argh wrong web site sorry its been a 21 hour stretch but the site I saw had different wiring

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