DP83825I: BIST Control Register (BISCR) Data for external loopback mode

Markus Theil

Part Number: DP83825I
Other Parts Discussed in Thread: DP83867IR, DP83825

What do i have to write in the BISCR to set the PHY in the external loopback mode?

The data sheet of the DP83825I says that the PRBS Built-in Self-Test (BIST) can be performed using both internal loopbacks (digital or analog) or external loopback using a cable fixture.

However its not being described how to address the register (BISCR). For example in the data sheet of the DP83867IR they say that the bits 5:2 of the BISCR must set to 0100 to perform

in the external mode.

Thank you for your help

over 1 year ago

0 Gokul Koraganji over 1 year ago

TI__Mastermind 19150 points

Hi Markus,

Firstly, what is the speed you intend to use for DP83867?

External loopback is only valid for 10M and 100M modes. For 1000M mode, external loopback can't be realized as transmit and receive happen on the same lines.

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Regards,
Gokul.

0 Markus Theil over 1 year ago

Prodigy 20 points

Hello Gokul,

I am using the DP83825I with 100M. I only mentioned the DP83867 as a comparison. In the data sheet of the DP83867 it is being described how to address the BISCR for external loopback. In the data sheet of the DP83825I (which i am using) is nothing mentioned about how to address the BISCR for external loopback.

Regards

Markus

0 Gokul Koraganji over 1 year ago in reply to Markus Theil

TI__Mastermind 19150 points

Hi Markus,

I will have to check why DP83867 needs register write to enable external loopback.

But, I am aware that, on DP83825, no register programming is needed to enable external loopback, if register 0x0000, 0x0019 are programmed appropriately.

--
Regards,
Gokul.

0 Gokul Koraganji over 1 year ago in reply to Gokul Koraganji

TI__Mastermind 19150 points

Hi Markus,

I've learnt that DP83867 needs register write to enable external loopback for 1000Base-T mode. Since 1000Base-T is defined over full duplex copper lines, a few parameters internally have to be changed to enable external loopback.

However on DP83825, since the copper lines are only half-duplex, no additional register settings are required.

--
Regards,
Gokul.

0 Markus Theil over 1 year ago in reply to Gokul Koraganji

Prodigy 20 points

Hi Gokul,

thank you for your help.

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DP83825I: BIST Control Register (BISCR) Data for external loopback mode