DP83869HM: How do I disable link loss pass through

John David Anglin

Part Number: DP83869HM

Our board has no connection to the RX_CLK pin. The OPCODE config pins set the opcode mode to 1. After re configuring to 1000BASE media converter mode, our board behaves as if link loss pass through is enabled. Disconnecting either port brings the other port down. However, the register setting for register 0x1EC appears to indicate that link loss pass through is disabled.

I changed bit '0' of register 0x1EC on and off but this didn't affect the behavior of the board.

Here is register dump:

0x000: 0x1140 0x7969 0x2000 0xa0f1 0x0001 0xcde1 0x006f 0x2001
0x008: 0x4006 0x0200 0x3800 ...... ...... 0x401f 0x616d 0xf000
0x010: 0x5048 0xbf02 0x0000 0x5c40 0x29c7 0x0000 0x0000 0x0040
0x018: 0x615b 0x4004 0x0002 ...... ...... ...... 0x0012 0x0000
0x020: ...... ...... ...... ...... ...... 0x0480 ...... ......
0x028: ...... ...... ...... ...... 0x141f 0x0000 0x0221 ......
0x030: ...... 0x10b0 0x00d0 0x0000 ...... ...... ...... 0x0003
0x038: ...... 0x0000 0x0000 ...... ...... ...... ...... ......
0x040: ...... ...... ...... 0x07a0 ...... ...... ...... ......
0x048: ...... ...... ...... ...... ...... ...... ...... 0x0166
0x068: ...... ...... ...... ...... ...... ...... 0x021c ......
0x080: ...... ...... ...... ...... ...... ...... 0x0077 ......
0x130: ...... ...... ...... ...... 0x1000 0x0000 ...... ......
0x170: 0x0c0f ...... ...... ...... ...... ...... ...... ......
0x180: ...... ...... ...... ...... ...... ...... ...... ......
0x188: ...... ...... ...... ...... ...... ...... ...... ......
0x190: 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000 0x0000
0x198: 0x0000 0x0000 ...... ...... ...... ...... ...... ......
0x1a0: ...... ...... ...... ...... 0x0000 0x0000 0x0000 ......
0x1d8: ...... ...... ...... ...... ...... ...... ...... 0x0044
0x1e0: 0x417a ...... ...... ...... ...... ...... ...... ......
0x1e8: ...... ...... ...... ...... 0x1ffd ...... ...... ......
0xc00: 0x1140 0x616d 0x2000 0xa0f1 0x0020 0x4060 0x0007 0x2001
0xc08: 0x0000 ...... ...... ...... ...... ...... ...... ......
0xc10: ...... ...... ...... ...... ...... ...... ...... ......
0xc18: 0x01ff 0x0011 ...... ...... ...... ...... ...... ......

Is there another register value that needs to change to disable link loss pass through?

over 3 years ago

0 Geet Modi over 3 years ago

TI__Mastermind 26320 points

Hi,

Let me look in and get back.

Regards,
Geet

0 John David Anglin over 3 years ago in reply to Geet Modi

Intellectual 260 points

I found yesterday by trial and error that clearing register 0x1EC disables link loss pass through. Previous discussions had indicated bit '0' controls this feature but that doesn't appear to be the case.

0 Geet Modi over 3 years ago in reply to John David Anglin

TI__Mastermind 26320 points

Hi,

0x01EC, bit 0 is the right register to enable/disable link loss pass thru. You shall be able do this thru strap configuration.

Regards,

Geet

0 John David Anglin over 3 years ago in reply to Geet Modi

Intellectual 260 points

I'm puzzled. After more testing, it appears to me that register 0x01EC, bit 3 enables/disables link loss pass thru in 1000BASE media converter mode.

It would help to have documentation for register 0x01EC.

With the board I have, it's not easy to use strap configuration.

0 Geet Modi over 3 years ago in reply to John David Anglin

TI__Mastermind 26320 points

Hi,

My bad in earlier response. It's bit 3 of 0x1EC register to enable and disable Link Loss Pass thru feature.

Regards,
Geet

0 John David Anglin over 3 years ago in reply to Geet Modi

Intellectual 260 points

Hi Geet,

This is a follow up.

With the link pass thru feature disabled in 100BASE media converter mode, the PHY doesn't set the link status bits in BMSR and PHY_STATUS when there is no FX link. Yet, the other end thinks it is linked, and the LED0 is on and flashes when frames are received.

With the link pass thru feature enabled in 100BASE media converter mode, loss of link on the copper side does not cause link to drop on the optical side. The behavior is symmetric in 1000BASE media converter mode.

0 Geet Modi over 3 years ago in reply to John David Anglin

TI__Mastermind 26320 points

Hi John,

1. In MC mode, The copper side address are at 0x00... while Fiber register address starting from 0x0C00. I hope you are looking at right regiser set.

2. The Link Loss pass thru is been tested and expected to work. Can you share setup details and procedure for testing the Link Loss pass thru.

Regards,

Geet

0 John David Anglin over 3 years ago in reply to Geet Modi

Intellectual 260 points

Hi Geet,

I did some more testing.

There weren't any problems with the registers.

Regarding the PHY's failing to set the link status bits, I found that restarting auto-negotiation after setting/clearing the link loss pass through bit helped.

Regarding the link loss pass thru in 100BASE mode, the problem was in the media converter used for testing. FEFI detection was disabled. A pair of units with DP83869HM work fine in 100BASE media converter mode.

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DP83869HM: How do I disable link loss pass through