# Auto MDI-X difficulties with CC9P9215

**URL:** <https://forums.digi.com/t/auto-mdi-x-difficulties-with-cc9p9215/14492>\
**Category:** NET+OS\
**Tags:** connectcore9p9215, phy, automdi-x, netos\
**Created:** [March 6, 2015, 8:26am UTC](https://forums.digi.com/t/auto-mdi-x-difficulties-with-cc9p9215/14492 "2015-03-06T08:26:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![kay](https://avatars.discourse-cdn.com/v4/letter/k/ed655f/32.png) [@kay](https://forums.digi.com/u/kay)\
**Post date:** [March 6, 2015, 8:26am UTC](https://forums.digi.com/t/auto-mdi-x-difficulties-with-cc9p9215/14492/1 "2015-03-06T08:26:07Z")

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We have been using the CC9P9125 for years now always thinking it would perform Auto MDI-X on the Eth interface. Now a customer complains about it so we started testing. It seems it doesn’t work at all. We needed to use a crossover cable in direct connection to one of our older Computers here.  
The BSP code in MII.c suggest that the bit for the ICS Phy is set to auto (Register 19). However I am a bit concerned that it might be a problem that the code only notes 1893B while there is actually a 1893C on the boards, so maybe the auto detect fails.

We use Net+OS 7.3. but we also tried the fresh-out-of-box modules (with the plain ftp programming software) and they also didn’t responded on a 1:1 patch cable.

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**Author:** ![LeonidM](https://avatars.discourse-cdn.com/v4/letter/l/d26b3c/32.png) [@LeonidM](https://forums.digi.com/u/LeonidM)\
**Post date:** [March 6, 2015, 5:37pm UTC](https://forums.digi.com/t/auto-mdi-x-difficulties-with-cc9p9215/14492/2 "2015-03-06T17:37:03Z")

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auto MDI-Xis disabled in all Digi modules due to compatibility issues with some Cisco routers. It is disabled both in Hardware and software.

Auto-MDI/MDIX is automatic, but may be disabled for test purposes using the AMDIX\_EN pin or by writing MDIO register 19 Bits 9:8 in the MDIO register. The \> Auto-MDI/MDIX function is independent of Auto- Negotiation and  
preceeds Auto-Negotiation when enabled

Holding (Pin 10) AMDIX\_EN low will disable the Auto\_MDIX function and force pins TP\_AP and TP\_AN to be the transmit pair and TP\_BP and TP\_BN to be the receive pair. AMDIX\_EN has a built in 50K Ohm internal pull-up.

cc9p9215 has populated R89 0 ohm resistor connecting AMDIX\_EN to GND effectively disabling Auto-MDI/MDIX