[ibis-macro] Eye mask definition for IBIS-AMI
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 1 Mar 2012 04:43:26 +0000
Hello everyone,
We had a few conversations on this topic in the past on this
email reflector and also in the IBIS-ATM meetings, but the
discussions didn't result in any actions as far as the
specification is concerned. I would like to bring this
topic up again because to me it seems that we have an
incomplete "solution" for this in the IBIS specification.
Currently, we have an AMI parameter in specification called
"Rx_Receiver_Sensitivity". Pg. 147 describes this parameter
like this:
| Rx_Receiver_Sensitivity can be of Usage Info and Out and of
| Type Float and of Data Format Value, Range and Corner.
| Rx_Receiver_Sensitivity tells the EDA platform the voltage
| needed at the receiver data decision point to ensure proper
| sampling of the equalized signal.
In other words, this is basically the Vinh and Vinl of the
core's input stage that is connected to the output of the Rx
buffer which contains all the fun stuff, the filter(s), DFE,
CDR, etc... Since the AMI simulation's output waveform goes
into this input, the eye opening we get from the AMI simulations
better be above and below +/-Rx_Receiver_Sensitivity, otherwise
this input stage will not be able to interpret the signals
correctly.
However, there is nothing in the AMI specification which would
help us to evaluate the timing relationship requirements between
these waveforms and the clock ticks. In other words, we have
no information about what the setup and hold times are supposed
to be around the sampling point for this input stage to recognize
the signal correctly.
To me it would make sense to define a complete eye mask which
would include a definition for the width of the eye (time) and
its time relationship to the clock ticks as well as for its
height (voltage). I would be willing to write a BIRD for this,
but before I begin, I would like to have a little brainstorming
session to collect some ideas on how people would deal with this
and what we should put into the specification.
As a bare minimum, I would like to propose a set of parameters
which defines the shape of a diamond, laying on its side:
*********
* *
* *
* *
* *
* *
*********
For the voltages we could have a high/low level and DC offset
and for the timing we could have a left/right corner and
the beginning and end points of the horizontal lines. This
could be achieved with seven parameters.
I could see a few additional parameters for a more elaborate
definition, but for now I will leave it at that.
Questions, comments welcome.
Thanks,
Arpad
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