RE: [10GBASE-CX4] SIGNAL_DETECT
Hi Shawn,
I agree with you on the premise that the received eye at the
MDI will be substantially closed (if not completely) and so
that leaves us a few options.
1) Spec input power. We have a LOT of power relative to noise
so you could cite a minimum threshold here with a lot of margin
but because power is an "average over time",you probably need to
spec a reasonable amount of time to ensure adequate spectral
distribution. Testing might be a bit complex, perhaps not.
2) Spec input voltage as it is done in 100BASE-T where you cite
a threshold above which the signal must rise to meet the "ON"
spec, then must stay below for some amount of time to meet the
"OFF" spec.
This works if you can guarantee that even an unequalized signal
will exceed the threshold at the end of the cable. For 100T, it
was made easier by the fact that the IDLE stream contained a
pulse which was 10bits wide. That pulse had a lot of amplitude
at the end of the cable. The time-period defined was long enough
to ensure that an IDLE sequence would occur.
I think we could implement #2 by simulating an IDLE sequence and
evaluating the eye opening, then setting the "OFF" timer duration
at 2x max packet + IPG time value. Even if the eye is closed, the
amplitude of some IDLE symbols will very likely exceed a voltage
based upon their deterministic content.
Dan
-----Original Message-----
From: Rogers, Shawn [mailto:s-rogers@ti.com]
Sent: Monday, January 27, 2003 11:02 AM
To: 10GBCX4
Subject: RE: [10GBASE-CX4] SIGNAL_DETECT
My $0.02:
I do not see how SIGNAL_DETECT can be specified in terms of a receiver
sensitivity threshold when, based on data presented, the receive eye will
likely be completely closed.
Even if not completely closed, there is a high likelihood that the receiver
min threshold will be so low that, even after EQ, you will not be able to
accurately apply a level test to determine whether there is adequate signal
to make a decision.
I believe the right approach lies in using the state machines provided in
Clause 48 to declare a Local Fault condition.
Shawn
____________________________________________
Shawn Rogers, PMP s-rogers@ti.com
High Speed Serial Link Marketing
Texas Instruments
12500 TI Boulevard / M/S 8732/ Dallas, Texas 75243
Office: 214.480.2678 Cell: 214.549.4868
______________________________________
-----Original Message-----
From: Petre Popescu [mailto:popescu@mail.quaketech.com]
Sent: Monday, January 27, 2003 12:16 PM
To: 10GBCX4
Subject: [10GBASE-CX4] SIGNAL_DETECT
Howard,
Please find attached the text proposed for SIGNAL_DETECT.
I found the most appropriate text for our applications in clause
39 (1000BASE-CX).
Regards, Petre
--
Petre Popescu
Quake Technologies
613.270.8113.x2229
613.220.8982 (cell)