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DP83TC814S-Q1: What is the clock frequency of TX when using RGMII?

zhijie lin
Prodigy 20 points
Part Number: DP83TC814S-Q1

Tool/software:

Hello TI Team,

1.What is the clock frequency of TX when using RGMII, and is there any difference in link up and link down states respectively?
2. I got the following information by reading the registers, bit13=1 in register 0x00, does it mean that it is currently in 100Mbps mode, i.e. the clock frequency is 25MHz?

3. I get the following information by reading the registers, 0x01=0061, where the values of [15:11] are all 0. Is this contradictory to point 2, please explain it to me?

Best Regards!

Lin Zhijie

  • 0
    TI__Mastermind 25362 points

    Hi Lin,

    1. TX_CLK is output of the MAC. Please ensure the MAC is providing 25Mhz clock to PHY on TX_CLK signal. PHY RX_CLK output is 25Mhz, regardless of link up/link down.

    2. In 100Mbps RGMII, RX_CLK and TX_CLK is 25Mhz. The clock speed is different for 10Mbps and 1000Mbps, but DP83TC814 supports only 100Mbps, so clock speed is always 25Mhz

    3. As you can see, bits [15:11] of register 0x1 are all 0 and are read only. This means the PHY does not support any speed other than 100Base-T1.

    Thanks,

    David