DP83848C: Communication abnormality

Hi Seishin,

How many times are you reading the BMSR register? The BMSR register is a latch low configuration which means you should read more than once to get the current status.

If the link has dropped since last reading bit[3], it will always return a 0.

You could also be dropping the link briefly such that you do not see a change in LED indication to the eye but BMSR will latch the bit low to show you a drop did occur in the past.

Best Regards,

Hi Rob-san,

Thank you very much for considering this question.

I am also working with Seishin on this issue.

With regard to your question we have requested our customer to get more details,
but we got below details from the customer.

In the customer's application, when there is a data input through PHY,
the MCU(MAC) recognizes that data and starts transmitting that data.

So during this issue, the MCU(MAC) properly recognizes the input data,
which means data receive operation is complete and the MCU tries to send that data
through PHY, but the PHY hangs up when transmitting that data.
i.e data reception works fine but PHY hangs up during transmission(also we see improper LED).

We would like to know if there is any information about the similar case
where PHY cannot send the data output (hang up).
If necessary we can send you detailed pulse mask data.
And as discussed with Aniruddha-san below the customer has requested for a design review.
e2e.ti.com/.../2061778

We have received schematic and gerber file from our customer which we can
send you offline...Could you please help us in reviewing the customer's board design?
Please do accept my friendship request.

Thank you.
Best Regards,

Hello Matsumoto-san,

I have accepted the connect request and sent you a private message with my contact details. Please forward me the customer schematics.

You mentioned that you see improper LED function. Do you mean that when the PHY starts transmitting, the Link LED goes off?

-Regards,
Aniruddha

Hello Aniruddha-san,

Thank you very much for accepting my friendship request.

I will send you the customer schematics via private message.

The Link LED goes on when the PHY starts transmitting and the Link LED of facing hub goes on, too.
We think TD+/TD port may out idle signal.

Thank you.
Best Regards, Tadaaki Matsumoto

Hello Matsumoto-san,

I am just leaving a note here that the issue is being handled offline over email.

-Regards,
Aniruddha