Re: [10GBASE-CX4] clause 54
Petre.
Yes, at first glance, it appears that the initial first baud of peaking
is longer than one baud, but it really isn't. To understand how I might
be able to say this, I'll first explain how I generated the mask.
I generate the mask with an excel spreadsheet. The parameters I have
are:
1) amplitude = first baud peak value
2) deviation from amplitude = amount that the upper mask and lower mask
are above and below the peak.
3) alpha = amount of emphasis, where Vout = X(n)/(1+alpha) -
X(n-1)*alpha/(1+alpha)
4) devation from alpha = amount that alpha can vary, where the upper
peak mask to lower plateau mask emphasis amount is above alpha by the
deviation from alpha and likewise for the lower peak mask to upper
plateau mask.
5) delta in time that the lower mask starts it's first rising edge after
the upper mask's first rising edge.
6) max transistion time = time it takes the transition to go from 20% to
80%, where the transition is the start of the upper mask's first rising
edge to the end of the lower mask's first rising edge.
7) min transition time = similar to the max except use the lower as the
starting point and the upper as the ending point.
8) Set the deviation in alpha and the peak such that the upper mask's
peak to lower mask's peak is the same as the upper mask's plateau to the
lower mask's plateau.
A real differential signal will not follow the upper or lower masks, it
will be somewhere inbetween. Looking at the start of upper mask rising
edge to the start of the lower mask falling edge there is one baud
time. A real signal will be delayed from these points by basically the
same amount. Yes, there can be rising edge to falling edge delay
differences even in a differential system but they are usually very
small, if any.
I'll have the spreadsheet in Vancouver and will step through it with
anyone that wants to. If we have time we can even go through it as a
group. I would put this as a low priority because this current mask is
100% generated and what we actually need is to see how some real silicon
fits to this or some other similar mask.
Howard
Petre Popescu wrote:
>
> Howard,
> The transmit template, Figure 54-6, shows the emphasis
> extending outside one bit time. Our simulations have shown
> a significant jitter increase in the received eye when the tail
> of the emphasis in the next bit is more than 10%.
> Regards, Petre
>
> --
> Petre Popescu
> Quake Technologies
> 613.270.8113.x2229
> 613.220.8982 (cell)