DP83640: About 83640 link status: BMSR bit2 and PHYSTS bit0

xiaoP

Intellectual 365 points

Part Number: DP83640

I read back the two reg to make sure link status. The BMSR bit2 is 0 and PHYSTS bit0 is 1. So which status is right?

I check the EPL lib the EPLIsLinkUp funtion, only read the PHYSTS bit0. So dont care BMSR bit2?

thanks guys

over 8 years ago

0 Aniruddha Khadye over 8 years ago

TI__Mastermind 18425 points

Hello,

The BMSR link status register bit[bit2] is a latched low register bit. Please read it twice to get the correct value. Alternatively, PHYSTS register bit 0 can be used for link status indication as well.

-Regards,
Aniruddha

0 xiaoP over 8 years ago in reply to Aniruddha Khadye

Intellectual 365 points

Hi:
you mean the link already failed before I read it, and it latched low. So I read it twice, it is 1. And this means the link is good now?
I check the datasheet, it says this bit will be set after read:
The criteria for link validity is implementation specific. The occurrence of a link failure
condition will causes the Link Status bit to clear. Once cleared, this bit may only be set by
establishing a good link condition and a read through the management interface .
how do I know whether it is set by my read?
Thanks!

0 Aniruddha Khadye over 8 years ago in reply to xiaoP

TI__Mastermind 18425 points

Hello,

The BMSR link status will not be set if there is no link. Reading the it twice will not give you false positive answer. Another method is to check register 0x10[bit0]. This is also a link status bit but it is not latched low.

-Regards,
Aniruddha

0 xiaoP over 8 years ago in reply to Aniruddha Khadye

Intellectual 365 points

got it

Interface

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DP83640: About 83640 link status: BMSR bit2 and PHYSTS bit0