DP83848I: Application problems

Hi Zoey,

Is the PC the link partner in this test? Could you provide a block diagram of your test setup?

DP83848 <-ethernet cable-> PC?

Regards,

Alvaro

Hi  Alvaro,

Thanks for your reply! The steps are as below:

Step 1: set as adaptive and 100Mbps full duplex ， simplex and the system works well; When multiple ping packets are tested in half-duplex mode, the software may drop packets；

Step 2: When switching to 10M duplex and half-duplex, the system can't connect either.

Step 3: Reset the module, it works under 10M full duplex, but it will drop packets under 10M half-duplex; it won't work when using computer to switch to 100M. 

关于dp83848 10Mbps下不通问题.doc

Hi Zoey,

Thank you for the document. So 100Mbps full duplex is working but Half duplex and 10Mbps isn't? This is strange. Please allow me until end of week (04/26) to review your schematic.

Regards,

Alvaro

Hi  Alvaro,

Yes. Hope for your reply!

Hi Zoey,

Thank you for your patience. The schematic looks good, I don't see a reason why this should fail. Do we have access to the registers? If so could you check Register 0x15[7:0]. If the RX_ERCNT is 0 then the PHY isn't the one dropping the packets. Have there been any new findings on your end? Please let me know.

Regards,

Alvaro

Hi  Alvaro,

This is no problem of the register  0X15.Do u have any other advice? thanks!

Hi  Alvaro,

The customer has a new finding:

The pc-side is initially 10M to the module communication and it is no problem, when switching to 100M, the 0x01 register changes from 0x784D to 0x7849, and immediately changes to 0x784D, the network can be connected. However, it should still have 10M communication status, not switched to 100M 

And another case when switching from 100M to 10M is that :

The pc-side is initially 100M and there is no problem connecting the module. When switching to 10M, the 0x01 register changes from 0x784D to 0x7849 and then no longer changes

Hi Zoey,

So when you're originally connected to the PC at 10Mbps and switch to 100Mbps, the DP83848 briefly links down (Reg 0x1 = 7849) before linking back up at 100Mbps. This is the expected behavior.

Zoey Wu said:

However, it should still have 10M communication status, not switched to 100M 

What do you mean by this comment? Why should it still be at 10Mbps?

When the PC is connected at 100Mbps, there is no problem until the speed is switched to 10Mbps, in this case the DP83848 links down and never recovers. Could you make sure that Auto-negotiation is enabled on both the DP83848 and the PC? When you get into this stuck state, could you try writing Reg 0x0[9] = '1'? This will restart the auto-negotiation process.

Regards,

Alvaro