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Big Test MFG says our Ethernet Chip violates the IEEE standard - are they right?

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metrologist:
Edit: it is a test equipment manufacturer acting as a customer to evaluate one of our new products - they were simply trying to connect to the instrument through Ethernet using a cat3 cable probably wired with a modular 8P4C plug (1236), and there was no talking until they went to a cat5 8P8C. So would this be an implementation flaw?

=== fake news:
A big one you will all know and love says that because our Ethernet port (RJ45 plugs), has a design flaw because it does not support a cat3 cable (RJ11 plugs).

Does the IEEE standard actually state that the physically different plug must be supported?

wraper:
Title says it's the chip but it's about the port. What IEEE standard in particular? There are many. Sounds like utter BS, even latching mechanism is not compatible between them.

ve7xen:
Do they call out the clause and standard they think is being violated?

The only IEEE 802.3 PMA supporting Cat3 that would be relevant is 10base-T. Clause 14.5.1 of 802.3-2018 (in the 10base-T MDI section) says:


--- Quote ---Eight-pin connectors meeting the requirements of Clause 3 and Figures 1 through 5 of IEC 60603-7:1990 shall be used as the mechanical interface to the twisted-pair link segment. The plug connector shall be used on the twisted-pair link segment and the jack on the MAU. These connectors are depicted (for informational use only) in Figure 14–21 and Figure 14–22. The following table shows the assignment of signals to connector contacts.
--- End quote ---

So I don't see anything requiring the RJ-11 (6P2C, or the RJ14/RJ25 variants with more conductors) be compatible with the jack, and they specifically require an 8-pin connector (RJ11 etc. are 6-position), however I don't have access to IEC 60603-7:1990, which perhaps does specify a mechanical backwards-compatibility. This requirement also doesn't make sense in context, since pin 1 is used in 10base-T, and this outer pin is missing in RJ11, so you would never achieve a functional link using those connectors with any 10base-T or any other -T PMA; they all use pin 1.

wraper:
Also CAT3 does not mean 6 wires. It can easily have 8 wires or 200.

ejeffrey:
Definitely they should cite which standard and the specific section they think you are violating.  You should be able to look at the cited text to see if what they are claiming makes sense.

8P8C jacks are designed to (poorly) accommodate 6P/2C plugs and cables.  In some cases this was used to allow a combined ethernet/phone jack with the phone on pins 4/5 which are not used on 10baseT or 100baseT.  I guess somehow an 8P8C jack that can't physically fit a 6P2C cable plug might be in violation of the mechanical standard for the jacks.  I'm not sure exactly how you would make such a jack, and if you did I would consider it a feature since 1G networks use all 4 pairs and so plugging a phone in can't work, and any actual ethernet standard needs pin 1.

Cat3 is the cable standard, not the plug/jack.

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