DP83869HM: LINK_STS1 and LINK_STATUS_2 bits don't correctly indicate link status of copper port in media converter modes 4 and 5 when SFP (FX) side is not linked

John David Anglin

Intellectual 260 points

Part Number: DP83869HM

The setup is a follows:

1) Connect a pair of units back to back using copper.

2) Configure both PHYs to opmode 4 or 5.

3) Disable link loss pass through.

4) I have LED0 configured to mode 0xB (link activty).

5) Connect SFP interface on one unit to network packet source.

6) Leave SFP interface on the other unit disconnected.

This is status on unit with fiber connected:

OM1G Ethernet Media Converter
OM1G BootLoader 1.0 Jun 19 2020 12:02:58
OM1G Application 1.0 Jul 6 2020 17:37:02

Operation Mode: 1000BASE Media Converter
Link Loss Pass Thru: Disabled

OM1G Ethernet Configuration
Port Port        ANE Advertised Advertised Forced Forced
      Mode             Speed Bits Pause       Speed   Duplex
RJ45 Auto        On   100000      Off         1000    Full
SFP   1000BASE-X On   100000      Off         NA      NA

OM1G Ethernet Status
Port Link Auto         Mode/Speed   Duplex       MDI
      Good Negotiation
RJ45 Yes   Resolved     1000BASE-T   Full-Duplex MDI-X
SFP   Yes   Resolved     1000BASE-X   Full-Duplex NA

This is status on unit with fiber disconnected:

OM1G Ethernet Media Converter
OM1G BootLoader 1.0 Jun 19 2020 12:02:58
OM1G Application 1.0 Jul 7 2020 10:16:09

Operation Mode: 1000BASE Media Converter
Link Loss Pass Thru: Disabled

OM1G Ethernet Configuration
Port Port        ANE Advertised Advertised Forced Forced
      Mode             Speed Bits Pause       Speed   Duplex
RJ45 Auto        On   100000      Off         1000    Full
SFP   1000BASE-X On   100000      Off         NA      NA

OM1G Ethernet Status
Port Link Auto         Mode/Speed   Duplex       MDI
      Good Negotiation
RJ45 No    Resolved     1000BASE-T   Full-Duplex MDI
SFP   No    Enabled      1000BASE-X   Full-Duplex NA

The LED0 LED is on and showing link and network activity on both units.

Here is register dump from the unit with disconnected fiber:

0x000: 0x1140 0x7969 0x2000 0xa0f1 0x0001 0xc001 0x006f 0x2001
0x008: 0x4800 0x0200 0x3800 ...... ...... 0x401f 0x1ff5 0xf000
0x010: 0x5048 0xa802 0x0000 0x1842 0x29c7 0x0000 0x0000 0x0040
0x018: 0x615b 0x4004 0x0002 ...... ...... ...... 0x0012 0x0000
0x020: ...... ...... ...... ...... ...... 0x0480 ...... ......
0x028: ...... ...... ...... ...... 0x141f 0x0000 0x0221 ......
0x030: ...... 0x10b0 0x0050 0x0000 ...... ...... ...... 0x0000
0x038: ...... 0x0000 0x0000 ...... ...... ...... ...... ......
0x040: ...... ...... ...... 0x07a0 ...... ...... ...... ......
0x048: ...... ...... ...... ...... ...... ...... ...... 0x0220
0x068: ...... ...... ...... ...... ...... ...... 0x081c ......
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: ...... ...... ...... ...... 0x1ff5 ...... ...... ......
0xc00: 0x1140 0x6149 0x2000 0xa0f1 0x0020 0x0000 0x0004 0x2001
0xc08: 0x0000 ...... ...... ...... ...... ...... ...... ......
0xc10: ...... ...... ...... ...... ...... ...... ...... ......
0xc18: 0x01ff 0x0000 ...... ...... ...... ...... ...... ......

The SPEED_DUPLEX_RESOLVED bit is set indicating auto-negotiation has completed.

Why is link down on copper?

I have implemented SNLA305 on fiber side.

over 3 years ago

0 Geet Modi over 3 years ago

TI__Mastermind 26320 points

1. What happens when Fiber is connected as well ? Does it shows proper Link up on both units ?

2. Do you have signal detect signal from SFP connected to PHY ?

Regards,

Geet

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

Intellectual 260 points

Hi Geet,

When fiber is connected on both units, it shows proper Link on both units (copper and fiber).

The LOS signal from SFP is connected to pin 24 (JTAG_TDI/SD).

Regards,

Dave

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

Intellectual 260 points

Here is another oddity. I implemented a 100BASE media converter mode with auto-negotiation. With the fiber side linked, LED0 continues to show link/activity with the copper cable disconnected. The link status for the copper shows the link is down. When copper is connected to another unit with its fiber disconnected, LED0 show copper link activity but the link status for the copper is down.

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

Intellectual 260 points

Previous comment should have said "with auto-negotiation off".

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

TI__Mastermind 26320 points

What's the Signal Detect polarity of the SFP ? The PHY needs it active low.

Regards,

Geet

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

Intellectual 260 points

The signal available from SFP's is loss of signal (LOS). It is active high. Thus, the polarity is correct for direct SFP connection.

The schematic shown in SNLU237 has it connected directly.

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

TI__Mastermind 26320 points

Can you try it with changing to ACTIVE LOW on PHY.

Regards,
Geet

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

Intellectual 260 points

SFP output is low when optical signal is present. Should be correct. Can't easily be changed.

However, that brings up the question as to how the signal detect pin configures when the strap options are for 1000BASE media converter. LED_1 and LED-2 are pulled high on board. In RGMII to 100BASE-FX mode, pulling LED_1 high configures pin 24 as a signal detect pin. But does this apply to 1000BASE media converter mode?

Signal detect doesn't appear in STRAP_STS or OP_MODE_DECODE. Is there a way to configure it if necessary?

Is there a way to change signal detect polarity in PHY>

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

TI__Mastermind 26320 points

Hi John,

Signal detect is available on 1000Base as well same as 100Base-FX. Currently it's missing in datasheet and we plan to add this in next revision of datasheet.

For Changing the SD polarity, you can use following register 0x30 bit 2.

Regards,
Geet

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

Intellectual 260 points

Hi Geet,

I'm just going to look at this.

Is there a bit which enables/disables SD? If so, what is its definition?

Which SD polarity does setting register 0x30 bit to 1 correspond to?

Thanks,

Dave

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

Intellectual 260 points

I'm still seeing the same behavior with register 0x30 set to 0x0004.

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

TI__Mastermind 26320 points

What's the default value of the register ? Did you try swapping the bit 2 value while keeping the other bits same ?

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

Intellectual 260 points

The default value of register 0x30 is 0x0000. That's why I tried 0x0004.

I can see the state of the SFP's LOS line in the micro and it is behaving as expected. It is low with no optical connection and high when optics are connected. The link status for the optics also behaves correctly.

It's only the copper link status that is wrong when there is no optical signal.

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

TI__Mastermind 26320 points

Hi,

Default configuration of this bit is active Low.

Regards,

Geet

0 John David Anglin over 3 years ago

Intellectual 260 points

Thus, the issue with the copper link status bits is not directly related to the optical signal detect.

The optical link behaves normally.

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

TI__Mastermind 26320 points

This is impacted only when Link Loss Pass thru is enabled.

Regards,
Geet

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

Intellectual 260 points

No. This occurs when link loss pass through is disabled.

When link loss pass through is enabled, disconnecting the optical connection forces the copper link down. The LINK_STS1 and LINK_STATUS_2 bits are correct in this case.

Interface

Interface forum

DP83869HM: LINK_STS1 and LINK_STATUS_2 bits don't correctly indicate link status of copper port in media converter modes 4 and 5 when SFP (FX) side is not linked