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DP83822H: Link creation DP83822H Phy

Jan Bock
Intellectual 2690 points
Part Number: DP83822H

Hi, 

my customer has the following question regarding the linking of the DP83822H:

Within the scope of the EtherNet/IP certification it is necessary that the link can be firmly configured. As a minimum, the device must support autonegotiation, 100Mbit-FD and 10Mbit-FD. Now the remote station is left on autonegotiation during the test and it is expected that the link is established and the device is reachable, but this is not the case. Only after I change the configuration of the network interface on the PC and set it to a predefined speed, the link is established and the device is accessible again.

In the past they have used the phys and switches of a competitor. These have also established the link to the PC with a fixed link speed and deactivated autonegotiation. Can you set this in DP83822H Phy as well?

  • 0
    TI__Expert 5425 points

    Hi Jan,

    It is possible to set the DP83822H to a fixed speed with auto negotiation deactivated. This can be achieved through strap configurations (see section 8.5.1, table 12 of the datasheet) or writing to register 0x0000.

    Regards,

    Adrian Kam

  • 0 in reply to Adrian Kam
    TI__Intellectual 2690 points

    Hi Adrian, 

    they use the register 0x0000 to configure the phy. After the phy is configured, it stopped linking to the test system. It is needed that the phy connects to the test pc with the configured speed. So he ask if there are other registers that they have to set up?

    thanks

    Jan 

  • 0 in reply to Jan Bock
    TI__Expert 5425 points

    Hi Jan,

    To clarify, before configuring register 0x0000, you were able to establish link, which was then dropped after you wrote to the register? Or were you never able to establish link in the first place? When setting fixed speed and disabling auto-negotiation, writing to register 0x0000 should be the only needed register write. Can you provide the register data for registers 0x00 to 0x1F?

    Regards,

    Adrian Kam

  • 0 in reply to Adrian Kam
    TI__Intellectual 2690 points

    Hi Adrian, 

    The customer says that the device first get started  in default mode with autonegotiation through the strap in pins and the phy connects to the PC with 100Mbit. During initialization, they may set the link speed via register 0x0000 (e.g. to 10Mbit). Since the link is already there and it won't be reconfigured, they restart autonegotiation via the register 0x001F bit 14. This causes the link break down and the phy does not re-establish the link again. The expectation of the customer is that the link will be re-established with the new specified data rate. 

    Thanks 

    Jan 

  • 0 in reply to Jan Bock
    TI__Expert 5425 points

    Hi Jan,

    Is the customer trying to establish a fixed connection or a connection through auto-negotiation?

    For fixed mode, after setting the link speed, the customer also has to disable auto-negotiation in the same register. Otherwise, the bit will be ignored, and auto-negotiation will still occur and choose the best speed (100M in your case). Auto-negotiation can also be disabled through strap resistor settings as well. Duplex mode (bit 8 of register 0x0000) also needs to be configured to half or full duplex depending on the link partner. After configuring everything in register 0x0000, a link should be established at that fixed speed assuming the link partner is also capable of all the settings that are configured (speed and duplex mode). If not, try performing a digital reset by writing to bit 14 of register 0x001F. I would recommend changing the straps to configure the PHY in fixed mode so register writes are not necessary.

    For auto-negotiation mode, can you try writing to bit 9 of 0x0000 to restart auto-negotiation instead of writing to register 0x001F? Does the same issue occur?

    Another thing to double check is if the link partner is capable of establishing link with the fixed speed PHY.

    If you are still having trouble, can you provide the register data for registers 0x00 to 0x1F when you are trying to establish a fixed connection?

    Regards,

    Adrian Kam