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DP83TC811S-Q1: The RX-CLK sent by the PHY to the MAC will catch the 84Mhz waveform when it is powered on, and the 84Mhz frequency feels abnormal

Bao Songhao

Intellectual 560 points

Part Number: DP83TC811S-Q1

During debugging, I only connected the MDIO and reset between PHY and MAC, and did not connect the PHY,MAC's RX clock data and TX clock data directly. The TX-CLK sent by MAC to PHY can catch 125Mhz waveform, but the RX-CLK sent by PHY to MAC will catch 84Mhz waveform when it is powered on. The 84Mhz frequency feels abnormal. Is there something wrong with the PHY register configuration?

over 1 year ago

0 David Creger over 1 year ago

TI__Genius 17800 points

Hi Bao,

It sounds like this is related to your other post here: https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1118229/dp83tc811s-q1-1-during-the-debugging-we-found-that-the-25mhz-crystal-oscillator-would-start-to-vibrate-for-a-period-of-time-after-power-on-but-it-would-stop-later-i-don-t-know-what-is-the-cause-the-chip-goes-into-low-power-mo

The combination of these two issues leads me to believe the crystal and/or power-up timing specifications are not being met.

Please see the power-up timing part of section 7.6 of the datasheet, Figure 9 and 10, as well as the following crystal specs.

Thanks,

David