[ibis-macro] Re: RX Optimization
- From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
- To: Gregory R Edlund <gedlund@xxxxxxxxxx>
- Date: Fri, 8 Mar 2013 11:47:30 -0800
Greg,
That sounds correct.
-Ambrish.
From: Gregory R Edlund [mailto:gedlund@xxxxxxxxxx]
Sent: Friday, March 08, 2013 2:14 PM
To: Ambrish Varma
Cc: ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: RX Optimization
Ambrish,
The original question from my colleagues was simply whether or not the RX
algorithmic model considered TX equalization during optimization (link
training). I answered "yes" to them but wanted to understand the details of
where optimization occurs in the flow.
I believe you're telling me RX optimization can occur in one of two places,
depending on how the RX algorithmic model is constructed:
Step 3: RX AMI_Init
Step 7: RX AMI_GetWave
Did I understand your note?
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
[cid:image001.gif@01CE1C0B.DC529260]Ambrish Varma ---03/08/2013 12:47:49
PM---Greg, When I said that the simulators should not be expected to do
anything special, I meant that th
From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
To: Gregory R Edlund/Rochester/IBM@IBMUS
Cc: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
Date: 03/08/2013 12:47 PM
Subject: RE: [ibis-macro] Re: RX Optimization
________________________________
Greg,
When I said that the simulators should not be expected to do anything special,
I meant that they should not be treating the Tx in any special manner just
because the Rx is in training mode. They should still be providing a valid (or
as best as it can) impulse response and/or analog waveform to the Rx for it to
do its thing.
So to go back to the statement in your original email – generally, training in
the Rx occurs in the Getwave – and if the Tx AMI model also includes Getwave,
in time domain simulations, any Tx equalization in the Init is ignored.
However, if the Rx AMI model only has an Init function, it could include an
optimization algorithm and the simulator must provide the impulse response
*with* any Tx equalization to the Rx Init function.
I consider that ‘normal’ simulator behavior – and one that tries to mimic real
life.
Of course, there is a good chance that the Tx Init does not perform any
equalization as there is a Getwave in that model.
Sorry – I think I misunderstood your original question.
Thanks,
Ambrish.
From: Gregory R Edlund [mailto:gedlund@xxxxxxxxxx]
Sent: Friday, March 08, 2013 12:51 PM
To: Ambrish Varma
Cc: ibis-macro@xxxxxxxxxxxxx
Subject: Re: [ibis-macro] Re: RX Optimization
Amrish,
Thanks for your response. Do I understand correctly that you're disagreeing
with IBIS 5.1, which states:
"Under certain circumstances, for example when the Rx AMI_Init function
includes an optimization algorithm, the impulse response presented to the Rx
AMI_Init function must include the Tx equalization effects for the optimization
to work correctly."
Or are you saying that the simulator and the hardware do not behave the same
way?
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
[cid:image001.gif@01CE1C0B.DC529260]Ambrish Varma ---03/08/2013 11:38:00
AM---Hi Greg, Rx training, when you consider real devices, don't have any idea
how Tx's are behaving. In
From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
Date: 03/08/2013 11:38 AM
Subject: [ibis-macro] Re: RX Optimization
Sent by: ibis-macro-bounce@xxxxxxxxxxxxx
________________________________
Hi Greg,
Rx training, when you consider real devices, don’t have any idea how Tx’s are
behaving. In fact they don’t even know if there is any Tx equalization exist.
As such, there cannot and should not be any expectation that the simulators
should handle Tx equalization any differently during Rx training. The only
thing that the simulator has knowledge of is how many bits to ignore before it
starts gathering data for analysis purposes.
Glad you consider section 10 (or at least a part of it) clearly written ☺.
Thanks,
Ambrish.
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Gregory R Edlund
Sent: Friday, March 08, 2013 12:04 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] RX Optimization
Hello IBIS Comrades,
My co-workers and I were having a discussion today about how simulators should
handle TX equalization during RX training. I took an action item to run this
past the Open Forum and make sure I was speaking correctly.
"RX optimization (adaptive equalization), if it exists, occurs during Step 3,
i.e. the call to RX AMI_Init. During optimization the RX algorithmic model
must consider TX equalization, if it exists, and there is more than one way to
accomplish this. Two are documented in the IBIS 5.1."
By the way, Section 10.2.3.2 was clearly written. Most of our questions were
answered simply by reading two pages of the spec.
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
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