DM648 RSV resistor values

Bill Miller62523

Does anyone have know why the resistor values on the RSV 19, 20, 21, 22 pads are different on the Lyretech EVM from the DM648 data book values? We've been having problems with Ethernet comms on our custom board and I've just noticed that the RSV21 and RSV22 pads are right beside the SGMII pads, so the resistor values on these pads may be related to the SGMII operation.

over 14 years ago

0 B.C. over 14 years ago

TI__Genius 16906 points

Bill,

The EVM was likely designed before the datasheet was finalized. Please ensure that you are using the resistor values required by the datasheet.

Those RSV pins are not related to SGMII. The SGMII issue is more likely related to the layout of the SGMII interface. Please refer to the below SERDES layout guidelines (from C6455 SRIO) for proper implementation details:

http://focus.ti.com/dsp/docs/litabsmultiplefilelist.tsp?sectionId=3&tabId=409&literatureNumber=spraaa8a&docCategoryId=1&familyId=1397

Regards,

Brad

0 Bill Miller62523 over 14 years ago in reply to B.C.

Prodigy 60 points

Brad,

Thanks for the feedback. RSV21 & RSV22 are to do with the PCI port whic hwe don't use. I changed them anyway and it made no difference to our Ethernet problem. Our SGMII layout follows the guidelines perfectly with controlled impedance lines between the DM648 and the PHY. They're about 1" apart. The root of the problem is the need for a pull down on the TCK pin, as per TI Advisory note 1.1.4. I added this and the port started to behave itself instantly. On the move again!

Thanks,

Bill

0 B.C. over 14 years ago in reply to Bill Miller62523

TI__Genius 16906 points

Bill,

Good to hear that the problem was solved. Let us know if you have additional questions.

Thanks,

Brad

Processors

Processors forum

DM648 RSV resistor values