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DP83825I: Loopback mode

Oba
Genius 17855 points

Part Number: DP83825I

Hello,

My customer has some questions for DP83825I loopback mode.

Q1)
They want to evaluate their board with digital loopback mode. Is the below sequnce correct for set to the mode?

BMCR=0x2100
BISCR=0x0104
PHYRCR=0x4000.

Q2)
The last line in Q1 (PHYRCR=0x4000). Is this restart needed?

Q3)
In this digital loopback mode case, it means verifying the communication quality by sending data from the CPU side to the PHY?

Q4)
In this verification, is it possile to verify by checking Error Count value in BICSR1?
If possible, could you tell me how to do it? Is it OK to just read the resigster and check counter value in the bit15-8?

Regards,
Oba

 

  • 0
    TI__Mastermind 26791 points

    Hi Oba-san, 

    Q1) The above sequence is correct. 
    Q2) SW reset is not needed. I have observed that the loopback works without it, but please do a SW reset to ensure the device can refresh the state machine. 
    Q3) Yes, it is correct. 
    Q4) No, this is for PRBS checker. And this is to check PRBS signal coming into DP83825 from the MDI side. Usually, this checker utilizes the PRBS signal that is generated by DP83825 as a link partner. 
    Customer often use the MAC to send packets and check if the MII side is working when they utilize digital loopback. 

    Best,
    J