DP83822I: RMII 50Mhz Clock not output

gouki ono

Part Number: DP83822I
Other Parts Discussed in Thread: TMDSCNCD28388D

Please tell me about the RMII for dsp83822i.
The environment is the control card "TMDSCNCD28388D".

PHY is initially set to BootStrap for MII.(RMII_EN = 0, XI_50 = 0)
After startup, necessary GPIO and MDIO 0x0017 are changed to RMII (Master Mode) setting.
RMII Clock Select = 0
RMII Recovered Clock Async FIFO Bypass = 1
RMII Mode =1

I thought that the 50Mhz clock is automatically output from RX_D3 when I change from MII to RMII, but when I check with an oscilloscope, it does not seem to be output.

Is there some setting I need to do?

over 2 years ago

0 Rahul over 2 years ago

TI__Expert 8721 points

Hi,

To better understand your query, DP83822 is physically strapped to operate in MII mode, so when the PHY boots up the strap configuration is loaded to MII mode.

How are you configuring the PHY to be in RMII mode, is it through strap configuration? The PHY has to be power cycled or restarted for the new configuration to be loaded.

Regards,
Rahul

0 gouki ono over 2 years ago in reply to Rahul

Intellectual 320 points

Hi Rahul.

The Boot Strap cannot be changed since the control card is still the same.
I just changed the PHY status to RMII through MDIO.
The changes are the same as in the first post.
After setting, digital restart is applied.

Does this not produce 50MhzClock? Or am I simply missing a procedure?

0 Rahul over 2 years ago in reply to gouki ono

TI__Expert 8721 points

Hi Gouki,

I will look into your issue today and update on the thread.

Regards,
Rahul

0 gouki ono over 2 years ago in reply to Rahul

Intellectual 320 points

How about that?

0 Rahul over 2 years ago in reply to gouki ono

TI__Expert 8721 points

Hi Gouki,

Apologies for my delay in response.

In order to achieve RMII, 50-MHz Reference Clock both RMII_EN =1 and XI_50 =1 (RMII Clock Select = 1).

Regards,
Rahul

0 gouki ono over 2 years ago in reply to Rahul

Intellectual 320 points

Hi Rahul.

Does this mean that "RMII_EN =1 and XI_50 =1" is required to "output 50Mhz clock from PHY"?

I have confirmed that the 50Mhz clock is output from the PHY on a master RMII with 25Mhz input, with bootstrap settings "RMII_EN = 1 and XI_50 = 0" on a custom board that I created, in addition to the control card.

If the bootstrap is not RMII, does this mean that the PHY will not output 50Mhz clock unless "RMII_EN =1 and XI_50 = 1"?

+1 Rahul over 2 years ago in reply to gouki ono

TI__Expert 8721 points

Hi Gouki,

Just to make sure we are on the same page:
If RMII Master mode is configured through bootstraps, a 50-MHz output clock will automatically be enabled on RX_D3.

If this is not the case and you want to achieve, 50-MHz clock output from RX_D3, along with configuring RMII mode, you will have to configure RX_D3 as a clock source from bits[10:8] of register 0x0462 and bits [14:12] of register 0x0462 determines the reference.

Linking datasheet:
https://www.ti.com/lit/ds/symlink/dp83822i.pdf?ts=1671217634157&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards,
Rahul

0 gouki ono over 2 years ago in reply to Rahul

Intellectual 320 points

Hi Rahul.

Thank you very much. That is what I wanted to know.
If I had not set RMII in Bootstrap, I would have had to set 0x462.

I confirmed that I can set 0x462 in the control card and output.

Regards.

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DP83822I: RMII 50Mhz Clock not output