DP83869HM: SYNCE Recovered clock continuity

Alexey Tsirlin

Part Number: DP83869HM
Other Parts Discussed in Thread: AM625

Tool/software:

Hi,

In case and I configure the CLK_OUT pin to output the recovered clock, what will happen if there is no link? Will it output internal clock or just output nothing? What happens during the transaction (from no link to link and vice varsa)? I am thinking of clocking the entire system (including the MPU) from the recovered clock (for SyncE operation) and I am wandering if there are any glitches on the CLK_OUT in this mode that can cause troubles with devices like MPU (AM625 like)?

Thanks!

Alexey.

9 months ago

0 Hillman Lin 9 months ago

TI__Mastermind 25955 points

Hi Alexey,

If you configure the CLK_OUT as a recovery clock. I believe you won't receive any clock signal when there is no link. Once the PHY establish the link, the recovery clock will be provided in the CLK_OUT pin.

In term of system level recommendation, we still recommend the MPU side to do a reset after the PHY establish the link to prevent any CLK glitches read due to the transition stage between steady stage to stable clock signal from the recovery clock.

Regards,

Hillman Lin

0 Alexey Tsirlin 9 months ago in reply to Hillman Lin

Prodigy 75 points

Hi,

This is what I was also thinking, but then I have came to the following thread: https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1091885/dp83869hm-dp83869-syne/4067817?tisearch=e2e-sitesearch&keymatch=dp83869#4067817

There is an example in that thread showing continuous clock even when there is no link. So I wanted to better understand how does this work...

Alexey.

+1 Hillman Lin 9 months ago in reply to Alexey Tsirlin

TI__Mastermind 25955 points

Hi Alexey,

Sorry for the confusion, I check it in the lab.

Yes you are correct, we are outputting transmitting clock signal when there is no link, and there will be some phase shift to lock up the recovery clock when the PHY is link up to another link partner.

Sincerely,

Hillman lin

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DP83869HM: SYNCE Recovered clock continuity