[ibis-macro] Re: What is the definition of Vref?

From: Walter Katz <wkatz@xxxxxxxxxx>
To: <Arpad_Muranyi@xxxxxxxxxx>, <ibis-macro@xxxxxxxxxxxxx>
Date: Fri, 31 Aug 2018 12:35:50 -0400 (EDT)

All,

Vref is an undefined and ill defined term "in this context". VrefDQ is
what is well defined for DDR5:

VrefDQ is a voltage that is determined by a register in the Rx that is set
by the controller. The output of the Gain Adjustment is the differential
voltage between DQ and VrefDQ.

If we want to decide that "in this context" means any AMI Single Ended
Channel (not necessarily DDR5/DQ), then we can define a more generic word
(e.g. Vref) to describe this voltage as the threshold voltage used at the
slicer to determine if a single is high or low. Unfortunately Vref is an
existing IBIS parameter (Timing specification test load voltage). So
VrefDQ in IBIS Speak ~ (Vinh+Vinl)/2, except the value of VrefDQ is
determined by simulation.

One suggested name for this is a new AMI Reserved Parameter Rx_Vref
defined as: The threshold voltage level that determines the value of a
single ended waveform.

If (voltage >  Rx_Vref+Rx_Receiver_Sensitivity)

Slicer_Output = 1

Elsefi(voltage <  Rx_Vref-Rx_Receiver_Sensitivity)

Slicer_Output = 0

Else

Slicer_Output = undefined

End

For DDR5 VrefDQ == Rx_Vref

Walter

Walter Katz

<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx

Office 978.461-0449 x 133

Mobile  720.417-3762

From: ibis-macro-bounce@xxxxxxxxxxxxx <ibis-macro-bounce@xxxxxxxxxxxxx> On
Behalf Of Muranyi, Arpad
Sent: Friday, August 31, 2018 11:18 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] What is the definition of Vref?

Hello Everyone,

As you may recall, we conducted a strawmen poll last week to help decide

what topics/issues need to be addressed in the IBIS-AMI specification.

The results have been posted to:

http://ibis.org/macromodel_wip/archive/20180828/bobross/IBIS_ATM_poll_resu
lts.zip

As you may see, Vref was on the top of the list.  As we started discussing
this

in our last teleconference, the question was raised:  what is the
definition of

Vref in this context.  I would like to solicit some feedback from all of
you to

help answer that question.  This would help to get a better idea on how
the

IBIS-AMI specification should be updated.

Please reply to this email with your thoughts, and/or come prepared to the

next ATM teleconference with suggestions or questions.

Thanks,

Arpad

==============================================================

References:
- [ibis-macro] What is the definition of Vref?
  - From: Muranyi, Arpad

[ibis-macro] Re: What is the definition of Vref?

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