DP83822IF: How to configure the MAC interface as RMII master or slave mode through pin strap?

John11513

Part Number: DP83822IF

Hi team,

About the MAC interface mode of DP83822, the datasheet says the device can work at RMII master or slave mode. However, it seems we can only select enable or disable RMII mode through pin strap. The datasheet does not say how to select master or slave mode.

Also, as my understanding, the device can only works in RMII master mode if the reference clock is generated from 25MHz crystal, and It can work in master or slave mode if it is clocked by 50MHz oscilator. correct?

Thank you,

John

over 5 years ago

0 Vibhu Vanjari over 5 years ago

TI__Genius 11900 points

Hello John,

To configure to RMII the straps required are RMII_EN and XI_50 both which are configured via the RX_DV pin. Selecting the RMII clock also configures to master or slave.

Please refer to the description of pin 23-XI, in the Pin Functions table, page 6 of the datasheet to understand the requirements for RMII clock in master and slave mode. In short the answer is yes.

Thanks,

Vibhu

0 John11513 over 5 years ago in reply to Vibhu Vanjari

TI__Expert 5720 points

Hi Vibhu,

Thank you for reply.

I understand the device can be set at RMII, 25MHz CLK mode through set RGMII_EN=0, RMII_EN=1, and XI_50=0. I am still confused how to select between master and slave mode. Is the device always working at master mode as long as XI_50=0?

Thank you!

John

0 Vibhu Vanjari over 5 years ago in reply to John11513

TI__Genius 11900 points

Hello John,

You are correct as long as RGMII_EN=0, RMII_EN=1, and XI_50=0, the PHY will operate in master mode.

Thanks,

Vibhu

0 John11513 over 5 years ago in reply to Vibhu Vanjari

TI__Expert 5720 points

So how should I do to configure it in slave mode? In other words, how device know wether it is configured for master or slave mode?

Thank you!

0 Vibhu Vanjari over 5 years ago in reply to John11513

TI__Genius 11900 points

Hello John,

RGMII_EN=0, RMII_EN=1, and XI_50=1

Thanks,

Vibhu

0 John11513 over 5 years ago in reply to Vibhu Vanjari

TI__Expert 5720 points

Thank you Vibhu,

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DP83822IF: How to configure the MAC interface as RMII master or slave mode through pin strap?