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DP83848k energy detect register settings

RM1
Prodigy 100 points


I would like a better understanding of the energy detect register settings and the bit functions.  In the application, an ethernet network will not normally be connected, so the goal is to have the PHY stay powered down and generate as little EMI as possible.

Energy detect burst disable:  "By default, Energy Detect (ED) transmits a burst of 4 ED data pulses each time the CD is powered up."

What is the CD?  What is the impact of disabling this?

Energy Detect Error Threshold:  What is an energy detect error event?  What is the typical setting for these four bits?

Energy Detect Data Threshold:  What is an energy detect event?  What is the typical setting for these four bits? 

When the device "takes actions," what actions are taken?

  • 0
    TI__Mastermind 18425 points

    Hello,

    When the Energy detect burst mode is disabled, the PHY transmits a single ED pulse instead of a burst of 4 pulses. It is recommended that ED Burst Mode is disabled by setting this bit. CD stands for collision detect.

    If the Energy detect circuit observes simultaneous signaling of opposite polarity on the Transmit and Receive pairs, then a error is recorded. The threshold for error detection event can be set by bits 7:4 of EDCR (0x1D). This threshold sets the number errors required for Energy Detect Event to be triggered. When the event is triggered, the ED_ERR_MET bit (bit 9) is set. No other action is taken. The default value for the 4 bits is 0x1.

    Just like for error event detection, bit 3:0 define the threshold for number of valid event for initiating power up from low power state. A valid event can be any MDI activity such as ED pulses or Link Pulses from a link partner. Once the threshold is met, bit 8 of EDCR will be set and the device will initiate power up sequence. The default value is 0x1 but for robust operation it is recommended to set the value to maximum (0xF).

    More information can be found in the application report SNOA462A (http://www.ti.com/lit/an/snoa462a/snoa462a.pdf).

    -Regards,

    Aniruddha