DP83869HM: Can I implement link loss pass through using registers?

Hi John,

Link loss feature can be be enabled by writing '0' to bit [0] of registers 0x1EC. This register is not in the datasheet right now but it will be included in the next revision of the datasheet. Please note that registers changes will be removed at every reset and power cycle.

-Regards

Aniruddha

Excellent!

I presume the bit should be '1' for all other modes.

Do you you know when the revised datasheet is expected?

Hi Aniruddha,

I asked whether there's a way to force the link down on the copper side because we typically provide independent link pass through for both the SERDES and MDI sides in out media converters.

Regards,

Dave

Hi Dave,

Do you need to have the ability to differentiate where the link loss originate from? That feature is not available on available on DP83869. Can you share how the ability to have separate Link Loss pass through  is used on a system? 

-Regards

Aniruddha

Hi Aniruddha,

I work as an electronics and software designer for Luxcom Technologies Inc.  Our OM1000 product uses a pair of switches to enable electrical and optical link pass through.  With a pair of units connected back to back, one can setup the link pass through to operate in one direction.  This somewhat simplifies locating faults.  One can also enable both switches to enable behavior similar to the DP83869HM.

The OM1000 uses a Marvell 88E1111.  It has a register bit setting which allows forcing the copper transmitter down.  The optical side is forced using TX_DISABLE.

We are designing a new unit based on DP83869HM.  We have a model that can be PoE powered and a model which can source PoE power.  The former is for industrial applications requiring fiber isolation and the later for powering security cameras, etc.

We have just starting testing the first prototype units and we hit a strange issue.  The OPMODE config pins were incorrectly set to mode 1.  I programmed the mode to 1000BASE media converter mode following the instructions in section 9.4.8.4 of the datasheet.  However, the unit failed to link.  It appears from running a cable test that pairs C and D were open.  We have just confirmed that the unit links when the OPMODE config pins are set to mode 4.  Something seems to t be missing from the 1000BASE media converter setup instructions.