Subject: [TICTOC] bi-directional SyncE - Copper GBE

From: "Ronen Solomon" <[email-masked]>
Date: Tue, 24 Mar 2009 04:32:40 +0200

Yaakov 

In the last meeting you raised the issue of supporting bi-directional
SyncE on Copper GBE. Can you please re-emphasis the problem and the
proposed solution.

Best regards

Ronen

---

From: Yaakov Stein <[email-masked]>
Date: Tue, 24 Mar 2009 19:33:47 +0200

Ronen,

The problem is that in 1000BaseT you need to use the same clock in both directions
(earlier copper physical interfaces used a different clock in each directions,
but with Gb that would lead to cross talk degrading the performance).

802.3-2005 states that when you use autonegotiation, the master is chosen randomly.
In fact, a random or pseudorandom number is generated for this purpose.

This would seem to prohibit the use of Gb copper for SyncE,
as the direction of the clock flow has a 50% chance of ending up wrong
(i.e. "upstream").

However, apparently the 802.3 people in their wisdom foresaw this problem.
They defined a control register bit (9.12) which forces a device to be master.
If both sides set this bit the autonegotiation fails, so if the link comes up
you can be sure the right side is master.

Y(J)S

From: [email-masked] [mailto:[email-masked]] On Behalf Of Ronen Solomon
Sent: Tuesday, March 24, 2009 04:33
To: [email-masked]
Cc: Rafi Ram
Subject: [TICTOC] bi-directional SyncE - Copper GBE

Yaakov

In the last meeting you raised the issue of supporting bi-directional SyncE on Copper GBE. Can you please re-emphasis the problem and the proposed solution.

Best regards

Ronen