New wave forms for SPI-3 Fig 44 & 45

Walter Bridgewater wally at eng.adaptec.com
Thu Jun 3 12:27:05 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* wally at eng.adaptec.com (Walter Bridgewater)
*
Gene,

My take on a worst case waveforms would be one that starts at a large
level and swings to a small level while changing polarity, and one that 
starts at a small level and swings to a large level, while changing polarity.

You take the difference in delays between the 2 types of waveforms to find
your input skew.  There are 4 different delays involed.

I went back and re-read 99-127r6 and it says nothing about a 4:1 ratio,
I thought it did.  It is important to test your reciever under a
worst case situation.  Using +100mV & -100mV as the amplitudes 
will not do that.  You need to test like 400mV to -100mV & -400mV to 100mV.  
(of course you still have to put the notch down to +-30mV into the 
waveform too).

99-127r6 does say that we should use amplitudes of +-100mV to +-800mV
(with fast edge rates) in the 3rd bullet on page 2.  I think
100-800mV swings are more than we will ever see, and should be 
limited to 100-400mV swings.  I thought that at the May 27th meeting,
somebody said and we all agreed that if there is more than a 4:1
ratio, then there is too much attenuation in the cable, and the cable
should be fixed.



I think we all agree that we account for any receiver offset after 
the waveforms.  (one way to account for offset would be to adjust the 
input levels, but there are several other ways to account for receiver 
input offsets.  Sorry if my brief sentence was confusing.)



Regards,
Wally



> 
> I replied to Alan - Yes. But Wally's answer below indicates the meeting may
> still be needed. You need to account for your offset but not by adjusting
> the 100 mV as the minimum starting point for the transition. If you do, as
> Wally has stated below, then we do not have agreement on the value since we
> concluded in the meeting that it was not necessary to specify or test what
> the specific receiver offset was. But it is necessary to specify what the
> input signal is allowed to be.
> 
> Gene
> 
> 
> 
> 
> 
> wally at eng.adaptec.com (Walter Bridgewater) on 06/02/99 09:11:11 PM
> 
> To:   alanl at lsil.com
> cc:   T10 at lsil.com (bcc: Gene Milligan)
> 
> Subject:  Re: New wave forms for SPI-3 Fig 44 & 45
> 
> 
> 
> 
> * From the T10 Reflector (t10 at symbios.com), posted by:
> * wally at eng.adaptec.com (Walter Bridgewater)
> *
> 
> Alan,
> 
> 100mV is the minmum signal level, it could start from 400mV.
> Also, you need to adjust this levels to include your receiver
> offset.
> 
> I hope the aztec addressing works
> 
> 
> Wally
> 
> 
> 
> >
> > * From the T10 Reflector (t10 at symbios.com), posted by:
> > * Alan Littlewood <alanl at lsil.com>
> > *
> > While we are on the subject of the receiver input waveform that Bill Ham
> was
> > sketching at the Colorado meeting, I would like confirmation that my
> > understanding of the sketch was correct.
> >
> > The signal swinging through +100 mV and -100 mV is the differential
> voltage.
> >  (-Signal -  +Signal).  Correct?
> > If not please clarify.
> >
> > Thanks,
> > Alan.
> >
> >
> >
> >
> >
> > Gene_Milligan at notes.seagate.com wrote:
> >
> > > * From the T10 Reflector (t10 at symbios.com), posted by:
> > > * Gene_Milligan at notes.seagate.com
> > > *
> > > Yes I agree with you if that is the conclusion the others reach unless
> > > someone is prepared to work on any related impacts to the transmitter
> > > specifications.
> > >
> > > Gene
> > >
> > > Wally Bridgewater <wally at eng.adaptec.com> on 06/02/99 04:25:22 PM
> > >
> > > To:   Gene Milligan
> > > cc:   T10 at Symbios.COM
> > >
> > > Subject:  Re: New wave forms for SPI-3 Fig 44 & 45
> > >
> > > Gene
> > >
> > > I didn't understand what that meeting was for, I thought it might be
> for
> > > something else.
> > >
> > > I thought we could all just look at our receivers with the 'notch' type
> > > waveform
> > > and say on the reflector whether we had any problems with it or not.
> > > If it turns out that everybody else also has no problem
> > > with the reciever mask, after having reviewed their simulations.
> > > Yes, I would say then that another meeting is not needed and we
> > > can wait until the July working group meeting to proceed with 99-127r6.
> > > We will have met the 2 week rule.
> > >
> > > Your right, figure 44 & 45 don't really show the receiver mask detail,
> so
> > > in
> > > other words, I have no problem with the receiver mask or any other part
> of
> > > 99-127r6.pdf
> > >
> > > Regards,
> > >
> > > Wally
> > >
> > > Gene_Milligan at notes.seagate.com wrote:
> > >
> > > > * From the T10 Reflector (t10 at symbios.com), posted by:
> > > > * Gene_Milligan at notes.seagate.com
> > > > *
> > > > Does this imply that from your standpoint the meeting  to review the
> > > > results of simulations with the proposed receive mask is not needed?
> > > >
> > > > Figures 44 and 45 do not have the required detail of the proposed
> > > receiver
> > > > mask so it is not clear if agreement with figures 44 and 45 indicate
> that
> > > > simulations support the proposed receiver mask.
> > > >
> > > > Gene
> > > >
> > > > wally at eng.adaptec.com (Walter Bridgewater) on 06/01/99 08:53:29 PM
> > > >
> > > > To:   T10 at Symbios.COM
> > > > cc:    (bcc: Gene Milligan)
> > > >
> > > > Subject:  New wave forms for SPI-3 Fig 44 & 45
> > > >
> > > > * From the T10 Reflector (t10 at symbios.com), posted by:
> > > > * wally at eng.adaptec.com (Walter Bridgewater)
> > > > *
> > > >
> > > > To Everybody,
> > > >
> > > > >From last weeks timing budget meeting in Colorado Springs,
> > > > I said I wanted to do some simulations with the new waveforms.
> > > >
> > > > We have looked at any timing issues that the notch in the
> > > > timing waveform might cause and haven't found any.
> > > >
> > > > So, as far as we are concerned, the new proposed waveforms
> > > > for figures 44 & 45 in the SPI-3 are okay with us.
> > > >
> > > > Regards,
> > > >
> > > > Wally
> > > > *
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