DP83TC811R-Q1: DP83TC811R-Q1 link-up issue

Hi Andy,

What is register 0x1 showing? When the PHY is not linking up, it means that the MDI connection (located at the TRD_M and TRD_P pins) are not connected properly to another device, or link partner.

I would like to understand more about your setup:

• Is this a custom  board?
• What is your PHY's link partner and what is your general system setup?
• Do you have a link LED in your design? Is it showing link?
• Could you provide registers 0x0-0x1F?

Best regards,

Melissa

Hi Melissa，

This is a custom board and the system is setup as:

• DP83TC811 is set as 100BASE-T1 slave mode and Autonomous mode.
• The PHY's link partner is Marvell's 88Q2112.
• The DP83TC811's link LED is used, but it's not blinking.

So far we have checked the following sections:

• DP83TC811's power supply and reference clock, which are OK;
• Apply hardware reset and check DP83TC811 is in normal state;

The design schematic and registers 0x0-0x1F value are attached below.

0x0 -- 0x60022100
0x1 -- 0x60060065
0x2 -- 0x600a2000
0x3 -- 0x600ea253
0x4 -- 0x60120001
0x5 -- 0x60160000
0x6 -- 0x601a0000
0x7 -- 0x601e2001
0x8 -- 0x60220000
0x9 -- 0x60262000
0xa -- 0x602a0100
0xb -- 0x602e1000
0xc -- 0x60320000
0xd -- 0x60360000
0xe -- 0x603a0000
0xf -- 0x603e0000
0x10 -- 0x60423085
0x11 -- 0x6046010b
0x12 -- 0x604ae400
0x13 -- 0x604e0200
0x14 -- 0x60520000
0x15 -- 0x60560011
0x16 -- 0x605a0100
0x17 -- 0x605e5a49
0x18 -- 0x60621810
0x19 -- 0x60660c00
0x1a -- 0x606a0010
0x1b -- 0x606e007d
0x1c -- 0x607205ee
0x1d -- 0x60760000
0x1e -- 0x607a0000
0x1f -- 0x607e0000

DP83TC811S.pdf

Hi Andy,

Register 0x1 seems to be showing link on the DP83TC811. Are you accessing register 0x133 using the correct extended register writes? These are the correct steps.

• Write 0xD=0x1F
• Write 0xE=0x133
• Write 0xD=0x401F
• Read 0xE

Is Marvell's 88Q2112 showing link as well? What is the speed set to? Is autonegotiation disabled? Is it set in the correct master/slave mode?

Best regards,

Melissa

Hi Melissa,

When DP83TC811 is unlink, the MDI sinal waveform is like:

It seems that the data signal is moduled by a 600kHz carrier. And when it's linkup, the MDI sinal waveform is like:

The register 0x133 value is 0x603a15f8，which is BIT_0,1,2 are zeros:

The Marvell's 88Q2112 is set 100base-t1 master mode,autonegotiation disabled, but it's LED is not blinking, which shows no link.

Hi Andy,

It is odd that only one side is showing link. 

• How are you probing the MDI signal, is this with single ended probes at either end of the connector?
• Are you able to link up with the 811 by itself (811 <---> 811)?
• Is the Marvell 88Q2112 able to link up with itself aswell?
• What is your CMC and connector part number?

Best regards,

Melissa