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DP83TC812S-Q1: Link down due to cable hot plug

Jass Jin
Intellectual 2475 points
Part Number: DP83TC812S-Q1

Tool/software:

Hi expert,

My customer is using 812 as slave. They found that there would be link down in hot plug 812s to the master device.

Link can recover by: re-plug, soft reset, re-config.

My question is why hot plug will cause link down, meaning in some case, 812s cannot auto-recover. When link down, SQI is always 0, is that link training is failed?

The other question is why re-plug can recover the link? How 812 detect the re-plug issue?

Thanks!

  • 0
    TI__Intellectual 2475 points

    Hi expert,

    Here is the register dumped when link down. The mode is not auto mode, will it cause link down in hot plug case?

    Fullscreen read-ethphy-ti812-all-regs.txt Download 
    
-------------------------------------------------------
Read phy registers @2024-09-03 02:36:48
MMD1F
[0]	[1]	[2]	[3]	=	2100	61	2000	a271
[10]	[11]	[12]	[13]	=	84	10b	44e8	cc
[15]	[16]	[18]	[19]	=	0	100	481d	c00
[1B]	[1E]	[1F]	[41]	=	0	0	0	88f7
[133]	[17F]	[180]	[181]	=	5f0	4028	0	0
[183]	[184]	[185]	[187]	=	0	203	a	100
[188]	[189]	[18A]	[18B]	=	80	40	40	1c0b
[18C]	[18E]	[300]	[301]	=	0	8004	2710	1703
[302]	[303]	[304]	[305]	=	45	419	30	4
[306]	[310]	[430]	[450]	=	a	0	770	2610
[451]	[452]	[453]	[456]	=	9	0	1	0
[457]	[458]	[45D]	[45F]	=	7e	0	0	c
[485]	[486]	[489]	[496]	=	1078	a05	1	44c
[497]	[4A0]	[523]	[553]	=	1c0	1000	0	2000
[560]	[561]	[562]	[600]	=	7e4	c07	fb	30
[601]	[602]	[603]	[608]	=	0	0	0	27a
[609]	[60A]	[60B]	[60C]	=	0	956	5	24
[60D]	[618]	[619]	[61A]	=	0	0	574	5dc
[61B]	[61C]	[61D]	[61E]	=	7d	0	0	0
[620]	[622]	[623]	[624]	=	0	0	0	5511
[625]	[626]	[627]	[628]	=	0	0	0	0
[629]	[62A]	[639]	[63A]	=	0	0	31	0
[63B]	[63C]	[63D]	[63E]	=	0	17e	0	0
[648]	[649]	[64A]	[871]	=	120	1	10	0
[873]	[896]	[89E]	...	=	821	22ff	0

MMD1
[1000]	[1001]	[1007]	[100B]	=	0	0	3d	800
[1012]	[1834]	[1836]	...	=	1	8000	0

MMD3
[3000]	[3001]	...	...	=	0	0



-------------------------------------------------------
Read emac registers @2024-09-03 02:36:50
EMAC_0_EMAC_SGMII_PHY
[0x07C58300]	[0x07C58304]	[0x07C58308]	[0x07C5830C]	=	0x00000001	0x0000007B	0x00000092	0x00000032
[0x07C58310]	[0x07C58314]	[0x07C58318]	[0x07C5831C]	=	0x00000070	0x00000000	0x0000005F	0x00000002
[0x07C58320]	[0x07C58324]	[0x07C58328]	[0x07C5832C]	=	0x00000000	0x00000000	0x00000000	0x00000002
[0x07C58330]	[0x07C58334]	[0x07C58338]	[0x07C5833C]	=	0x00000000	0x00000000	0x00000000	0x00000000
[0x07C58340]	[0x07C58344]	[0x07C58348]	[0x07C5834C]	=	0x0000006A	0x00000018	0x00000001	0x00000000
[0x07C58350]	[0x07C58354]	[0x07C58358]	[0x07C5835C]	=	0x00000000	0x00000000	0x0000000F	0x00000000
[0x07C58360]	[0x07C58364]	[0x07C58368]	[0x07C5836C]	=	0x00000000	0x00000000	0x00000000	0x00000000
[0x07C58370]	[0x07C58374]	[0x07C58378]	[0x07C5837C]	=	0x00000070	0x00000012	0x00000000	0x00000000
[0x07C58380]	[0x07C58384]	[0x07C58388]	[0x07C5839C]	=	0x00000001	0x00000000	0x00000031	0x00000000
[0x07C583A4]	[0x07C583A8]	[0x07C583AC]	[0x07C583B0]	=	0x0000004F	0x00000000	0x00000000	0x00000000
[0x07C583B4]	[0x07C583B8]	[0x07C583BC]	[0x07C583C0]	=	0x000000FF	0x00000000	0x00000000	0x00000000
[0x07C583C4]	[0x07C583C8]	[0x07C583CC]	[0x07C583D0]	=	0x00000000	0x00000010	0x00000000	0x00000000
[0x07C583D4]	[0x07C583D8]	[0x07C583DC]	[0x07C583E0]	=	0x00000060	0x00000000	0x00000000	0x00000001
[0x07C583E4]	[0x07C583E8]	[0x07C583EC]	...	=	0x000000D4	0x00000001	0x00000040

  • 0
    TI__Genius 14006 points

    Hi Jass,

    Yes, if the 812 is in managed mode (autonomous disabled), the PHY will not link up until after register write. Autonomous operation can be enabled through SMI access by setting register 0x18B[6] = '1'. 

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    TI__Intellectual 2475 points

    Hi Melissa,

    Customer is using autonomous mode and forced polarity. They used connector with foolproof, so polarity is not an issue.

    They compared with competitor's PHY and only ours will have 1/50 chance to lock down. Do you have any sugguestions?

    Thanks!

  • 0 in reply to Jass Jin
    TI__Genius 14006 points

    Hi Jass,

    1. Can you check that the Open Alliance script is being programmed to the DP83TC812 for either slave or master mode? This is mentioned in section  3 of this app note: https://www.ti.com/lit/an/snla389b/snla389b.pdf?ts=1726178310290

    2. What is the link partner of the DP83TC812?

    3. Can you read register 0x871 multiple times while link is up? I want to check SQI when link is up. SQI is a measure of the signal to noise ratio on the line. 

    4. Can you also check the MDI Traces layout? We have some guidelines here:https://www.ti.com/lit/an/snla387/snla387.pdf?ts=1726178802259 

    The traces should be < 2 inches, have continuous GND underneath, have 100 ohm differential impedance matching. 

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    TI__Intellectual 2475 points

    Hi Melissa,

    When link is up, SQI is 7, when it's down, SQI is 0. Other things will be replied later, thanks!

  • 0 in reply to Jass Jin
    TI__Genius 14006 points

    Hi Jass,

    Thanks for providing this information. I wanted to see if there was low SQI, which can point to (but not rule out) issues with the design. 

    Just so I understand the behavior correctly, this is what  happens:

    1. Customer plugs in the DP83TC812 (slave) to unknown link partner (master)

    2. Customers powers on DP83TC812 and link parter

    3. There is a 1/50 chance it will not link up at all

    If they replace the DP83TC812 with competiiton part, it will always be successful.

    Can you also check if this occurs between two DP83TC812s or is it just the DP83TC812 and link partner (which part number you will provide later)?

    Best regards,

    Melissa

  • 0 in reply to Melissa Chang
    TI__Intellectual 2475 points

    Hi Melissa, they are using RTL9071, maybe it's because it can switch in 100M/1000M?

  • 0 in reply to Melissa Chang
    TI__Intellectual 2475 points

    Hi Melissa,

    Do we need to config auto mode in both master and slave mode?

    I see some comments about state machine? Does it mean in master mode we need send normal command fisrt and in slave mode we just need to config auto mode?

    Thanks!

  • 0 in reply to Jass Jin
    TI__Genius 14006 points

    Hi Jass,

    Yes, auto negotiation should be turned off and the speed should be forced to 100M on the RTL9071.

    Managed mode strap option is recommended to prevent the link-up process from initiating while the required software configuration. Can you confirm if the software configuration from this app note https://www.ti.com/lit/an/snla389b/snla389b.pdf?ts=1726178310290 is being used?

    If the PHY is in slave mode, you can use either autonomous or managed mode. 

    If the PHY is in master mode, you can also use either autonomous or managed mode. 

    Best regards,

    Melissa