Re: [10GBASE-CX4] SIGNAL_DETECT - A picture is worth ~245 words
Dan,
Including a picture will help defining the SIGNAL_DETECT and
having a table with minimum and maximum limits is good.
Regarding the values to be included, I would like the minimum
value (VSDD) to be lower (~40 mV pp) and the assertion time
maximum value (if needed) to be larger.
A 1010101010 signal is a valid 8B/10B code and the received
amplitude (assuming ~20 dB attenuation at 1.6 GHz) can be as
low as 75 mV pp. If we account for reflections and crosstalk
contributions, the worst-case minimum signal amplitude can
be as low as 40 mV pp.
Petre
"DOVE,DANIEL J (HP-Roseville,ex1)" wrote:
> Last one bounced. Too Large. New try.
>
> -----Original Message-----
> From: DOVE,DANIEL J (HP-Roseville,ex1)
> Sent: Monday, January 27, 2003 3:45 PM
> To: 'Howard A. Baumer'
> Cc: Rogers, Shawn; 10GBCX4
> Subject: RE: [10GBASE-CX4] SIGNAL_DETECT - A picture is worth ~245 words
>
> I am attaching a PDF shot at this.
>
> Dan
>
> -----Original Message-----
> From: Howard A. Baumer [mailto:hbaumer@broadcom.com]
> Sent: Monday, January 27, 2003 1:35 PM
> To: DOVE,DANIEL J (HP-Roseville,ex1)
> Cc: Rogers, Shawn; 10GBCX4
> Subject: Re: [10GBASE-CX4] SIGNAL_DETECT
>
> Dan,
> If we use the low freq. content of the IPG then the loss at those freq
> is
> going to be around 12-15db (for 312.5MHz los components are: ~6db from Tx
> eq.,
> ~6-9db from the channel). The Hf & Lf levels are within ~5dB (Rx eq takes
> up
> this slack) so the sig det thresholds would then be withn a factor of 2 (or
> less) of each other. The IPG will guarantee us that we will have some low
> frequency content so there will be something to check. If we look at the
> max
> packet size of 1600 Bytes (rounding to make it easy) then there is 400 bytes
> per lane which equates to 4000 symbols. Since thse could conceivably be the
> "1010.." pattern (valid 8B10B coded output) we would need to wait that time.
> 4000*0.32ns =1280ns.
> It becomes a trade off of the time used to get hysterisus to indicate
> signal loss versus the level we use to get signal on. The level to detect
> Hf
> will more than likely end up close to a noise threshold. Waiting a longer
> time
> (more like 4us to allow non-standard jumbo packets) is not that bad a
> compromise to get a bit more robust signal detect threshold.
>
> Howard
>
> "DOVE,DANIEL J (HP-Roseville,ex1)" wrote:
>
> > Howard,
> >
> > Your approach is similar to mine except you assume a worst
> > case "010101" pattern and I was willing to take advantage of
> > the fact that the IDLE pattern will contain more low-frequency
> > content and thus we could increase the amplitude of the
> > squelch. Your approach allows a shorter time-frame for
> > detection of the OFF state though.
> >
> > Dan
> >
> > -----Original Message-----
> > From: Howard A. Baumer [mailto:hbaumer@broadcom.com]
> > Sent: Monday, January 27, 2003 11:37 AM
> > To: Rogers, Shawn
> > Cc: 10GBCX4
> > Subject: Re: [10GBASE-CX4] SIGNAL_DETECT
> >
> > My $0.02,
> > I think Shawn has a good point here. The resultant receivers'
> > sensitivity
> > could end up quite low and therefore random noise could trigure a
> > SIGNAL_DETECT. If we were to use the CL 48 state machine fault sections
> > then
> > we presuppose there will always be a PMD and a PCS in the same Si.
> > Another way to look at the problem would be to look at what the
> > amplitude
> > of the high frequency signal would be (the "1010...", the transition
> > ..,0,1,...). Allowing for a loss of 16-20dB from transmit mdi to receive
> > mdi
> > then we could specify if the receive signal goes above -20dB of the
> > transmitted
> > signal SIGNAL_DETECT goes on and if it doesn't for 32ns after that it goes
> > off.
> >
> > Howard
> >
> > "Rogers, Shawn" wrote:
> >
> > > 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)
>
> ------------------------------------------------------------------------
> Name: SIGNAL_DETECT.pdf
> SIGNAL_DETECT.pdf Type: Portable Document Format (application/pdf)
> Encoding: base64