RGMII interface - Rx - Ok, Tx - ?

Hi,
I am using a board with RGMII interface and
facing some problems w.r.t reception(Rx) and
transmission(Tx) of packets. I am trying to
diagnose the problem.

Is it possible that a port of a RGMII interface
can work properly only for Rx(Receiving data) and not
for Tx(Transmitting data).

That is, whenever there is a problem/damage in
a RGMII interface, will it stop doing both reception
and transmission ?
Any ideas ?

Thx in advans,
Karthik Balaguru

On Nov 5, 2:14*pm, karthikbalaguru <karthikbalagur...@gmail.com>
wrote:
> Hi,
>
> Is it possible that a port of a RGMII interface
> can work properly only for Rx(Receiving data) and not
> for Tx(Transmitting data).

Yes. Especially if TxC is bad.

> That is, whenever there is a problem/damage in
> a RGMII interface, will it stop doing both reception
> and transmission ?

Damage? Odd choice of words. But anything is possible; you need to
understand the software too.


> Any ideas ?

Get the data sheet, a logic analyzer, a good software debugger and a
packet sniffer.

On Nov 6, 9:56 pm, LittleAlex <alex.lo...@email.com> wrote:
> On Nov 5, 2:14 pm, karthikbalaguru <karthikbalagur...@gmail.com>
> wrote:
>
> > Hi,
>
> > Is it possible that a port of a RGMII interface
> > can work properly only for Rx(Receiving data) and not
> > for Tx(Transmitting data).
>
> Yes. Especially if TxC is bad.
>
> > That is, whenever there is a problem/damage in
> > a RGMII interface, will it stop doing both reception
> > and transmission ?
>
> Damage? Odd choice of words. But anything is possible; you need to
> understand the software too.
>

The same software is working fine in another board
with RGMII interface. The problematic board
is able to receivethe packets but it is not transmitting any
packets. Initially suspected some setup configurations
and software, but it does not look like it. ARP entries,
the MAC addresses and IP addresses etc look fine.

> Get the data sheet, a logic analyzer, a good software debugger and a
> packet sniffer.

Using Wireshark(Ethereal) analyzer to log the packets
& to track the request-response flows.
Need to check if there is any specific register available
with RGMII interface that would convey if it is really sending
(transmitting) the packets out before deciding on this.

Lemme know if you have any tricks/ideas.

Thx in advans,
Karthik Balaguru

karthikbalaguru wrote:
> On Nov 6, 9:56 pm, LittleAlex <alex.lo...@email.com> wrote:
>> On Nov 5, 2:14 pm, karthikbalaguru <karthikbalagur...@gmail.com>
>> wrote:
>>
>>> Hi,
>>
>>> Is it possible that a port of a RGMII interface
>>> can work properly only for Rx(Receiving data) and not
>>> for Tx(Transmitting data).
>>
>> Yes. Especially if TxC is bad.
>>
>>> That is, whenever there is a problem/damage in
>>> a RGMII interface, will it stop doing both reception
>>> and transmission ?
>>
>> Damage? Odd choice of words. But anything is possible; you need to
>> understand the software too.
>>
>
> The same software is working fine in another board
> with RGMII interface. The problematic board
> is able to receivethe packets but it is not transmitting any
> packets. Initially suspected some setup configurations
> and software, but it does not look like it. ARP entries,
> the MAC addresses and IP addresses etc look fine.
>
>> Get the data sheet, a logic analyzer, a good software debugger and a
>> packet sniffer.
>
> Using Wireshark(Ethereal) analyzer to log the packets
> & to track the request-response flows.
> Need to check if there is any specific register available
> with RGMII interface that would convey if it is really sending
> (transmitting) the packets out before deciding on this.
>
> Lemme know if you have any tricks/ideas.
>

Be sure that you are transmitting a good (valid) packet. I was using
Wireshark for a very similar test and if the packet is not value, the
interface receiving it will throw it away without passing it up to
Wireshark.

I also had problems with a network switch not delivering the data to the
connection that the Wireshark machine was on, so the data was going onto the
network, but Wireshark didn't get it.

Also check the the tx_en and tx_er signals are good. The MAC might be
transmitting without the PHY sending on the data.

Scott



__________ Information from ESET NOD32 Antivirus, version of virus signature database 4581 (20091107) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

Check power integrity... especially for PLL supplys... And check signal integrity - these signals are fast...

PI/SI are common problems with these types of interfaces. Even on boards designed by so called professional engineers.