DP83867E: DPP83867E MDIO pullups and strapping settings

Aaron Spaete

Part Number: DP83867E

Team,

My customer has the following questions:

1) the pullup for the MDIO pin which should be either 1.5K or 2.2K max. I’m planning to use 8 of these parts on one Serial Management Interface BUS and providing a distributed pull-up such that the parallel combination of pull ups is ~1.5K. What is the recommended approach for connecting and laying out the SMI bus?

2) Another question I have is a confusing point in the data sheet for Autoneg Disable in Table 7 for strapping using RX_CTRL vs Auto-Negotiation Enable in Table 11.

Disabled appears “0” for the RX_CTRL strap but “1” for the Register setting. Could you confirm this is correct?

Regards,

Aaron

over 8 years ago

0 Aaron Spaete over 8 years ago

TI__Expert 4527 points

0 Rob Rodrigues over 8 years ago in reply to Aaron Spaete

TI__Mastermind 19780 points

Hi Aaron,

There is a DS draft update that will be posted in the next few days to modify the strap table you have shown. Mode 1 and Mode 2 for RX_CTRL will be N/A. Only mode 3 and mode 4 are applicable.

The SMI bus clock and data can be routed as desired, the low frequency will not make a large impact. I would suggest making the traces as short as possible and distributed to each device in a chain.

The strap is auto-negotiation disable and the bit name is auto-negotiation enable so the two options will be opposite of each other. The bit name in register 0x0 is IEEE defined and the strap name is our own convention. So if disable is 0, enable is 1 as you see in your device. This is correct.

Best Regards,

0 Aaron Spaete over 8 years ago in reply to Rob Rodrigues

TI__Expert 4527 points

This means I’ll need to change the RX_CTRL pin strapping populated with resistors for Mode 3 or Mode 4 as opposed to being left open, correct?

0 Rob Rodrigues over 8 years ago in reply to Aaron Spaete

TI__Mastermind 19780 points

Correct

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DP83867E: DPP83867E MDIO pullups and strapping settings