DP83867E: Strap workaround

Boris Fennema

Part Number: DP83867E

We developed the PCB before it was mandated to strap RX_DV, RX_CTRL pin - so we do not have strap enabled on that pin

(Pin 38)

I have found a link to a Linux driver which had the same issue and they recommend clearing the following bit in CFG4 - I quote:


The data manual for DP83867IR/CR, SNLS484E[1], revised march 2017,
advises that strapping RX_DV/RX_CTRL pin in mode 1 and 2 is not
supported (see note below Table 5 (4-Level Strap Pins)).

There are some boards which have the pin strapped this way and need
software workaround suggested by the data manual. 
Bit[7] of
Configuration Register 4 (address 0x0031) must be cleared to 0. This
ensures proper operation of the PHY.

If we do not have this what would the symptoms be ?

over 7 years ago

0 Geet Modi over 7 years ago

TI__Mastermind 26320 points

Hello,

Refer to response from Aniruddha in below thread.

e2e.ti.com/.../597807

Regards,
Geet

0 Boris Fennema over 7 years ago in reply to Geet Modi

Intellectual 510 points

Many thanks - I spoke to the previous designer and it turns out he was aware of this issue and had added the workaround.

So the workaround is in place but we are still seeing occasional POR issues -

As part of the state machine we do always do another auto-negotiation pass after POR to enforce the new settings and CFG4.7 is cleared as part of that set.

Should that be enough ?

B.

0 Ross Pimentel over 7 years ago in reply to Boris Fennema

TI__Mastermind 23675 points

Hi Boris,

That should be sufficient then since you are implementing a software override after the hardware latch.
This should be robust.

0 Boris Fennema over 7 years ago in reply to Ross Pimentel

Intellectual 510 points

Hi Ross,

We found that on certain power-ons the link was not up - we changed the state machine to monitor the PHY status for around 4 seconds and if the link was still not up (or up and in a speed /duplex we did not expect) we would renegotiate again. That fixed it (did 2000 power ons with link up each time, whereas before 1 in 30 was suspect.)

Best regards.

Boris

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DP83867E: Strap workaround