I have what may be an unenlightened question about DFE in a bit-by-bit
simulation of Fangi's (tx2,rx2 are init_only) simulation.
If the rx2 returns a separate afe and dfe transfer-function impulse how
does the EDA tool correctly align the rx2 dfe impulse (essentially
replacing the rx2 cdr function)? As far as I can tell, there is no IBIS-AMI
defined time relationship between the symbol alignment in the bit-by-bit
stimulus at the rx2 input and the corresponding impulse into rx2 in the
AMI_Init call. If the dfe equalization is not applied in the correct
alignment, less-than optimal results ensue. The EDA tool can of course
provide a cdr proxy for rx2, but how does it know how the recovered clock
aligns to the stored dfe impulse returned by rx2's AMI_Init?
Or am I missing something?
[I have long felt that the time relationship between an impulse in AMI_Init
and a bit-by-bit pattern in AMI_Getwave should be defined to make these
problems simpler]
regards,
Bob
On Mon, May 8, 2017 at 7:09 AM, Walter Katz <wkatz@xxxxxxxxxx> wrote:
Fangyi,
You have described a valid flow problem with one of the 81 cases that can
occur in IIS 6.1 models. And I agree that by adding additional IR outputs
to Rx and Tx AMI_Init (then there are 625 cases) these kinds of problem
goes can go away for if the model maker writes AMI_Init with the additional
IR output.
The point I have been trying to make is that when we implement in the
standard the optional ability to add these additional IR outputs to AMI
Init, in IBIS 7.x, then the flows will still need to support all 625 cases,
including the 81 cases in IBIS 6.1.
- Will not the 7.x flows need to describe the flows for these 81 case?
- Will not the flows for these 81 cases need to be the exact flows I
describe in BIRD 166.3?
I claim the answer to both of these questions must be yes. And if this is
the case then nothing I have written in BIRD 166.3 for IBIS 7.0 becomes
invalid for these 81 cases.
I repeat the question that you have not answered.
*What bad things happen if BIRD 166.3 is included in IBIS 7.0?*
Walter
Walter Katz
wkatz@xxxxxxxxxx
Phone 303.449-2308 <(303)%20449-2308>
Mobile 303.335-6156 <(303)%20335-6156>
*From:* ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@
freelists.org] *On Behalf Of *fangyi_rao@xxxxxxxxxxxx
*Sent:* Monday, May 8, 2017 4:17 AM
*To:* wkatz@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
*Subject:* [ibis-macro] Re: Fangyi and I had an AR to describe what bad
things can happen if IBIS 166.2 is approved in 7.0 and the Keysight BIRD
with additional IR is approved in IBIS 7.1 ...
(Resend with typo fixed)
All,
In the attached doc I showed that the BIRD166 flow may unphysically
amplify redriver nonlinearity, internal noise and crosstalks when they
reach downstream DFE and that this amplification equals the upstream
channel loss in dB. This problem can’t be resolved by incremental changes
in current flow. That’s why additional columns are added to impulse
response matrix in the Keysight BIRD.
BTW, there is no need to count the number of possible combinations. As
more aggressors and cascaded redrivers are added to the link, this number
will keep growing. The flow in the Keysight BIRD, described in a separate
doc, is designed in a scalable way so that one only needs to deal with 4
basic combinations and all others are automatically covered.
Fangyi
*From:* ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@
freelists.org <ibis-macro-bounce@xxxxxxxxxxxxx>] *On Behalf Of *Walter
Katz
*Sent:* Wednesday, May 03, 2017 11:40 AM
*To:* IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
*Subject:* [ibis-macro] Fangyi and I had an AR to describe what bad
things can happen if IBIS 166.2 is approved in 7.0 and the Keysight BIRD
with additional IR is approved in IBIS 7.1 ...
All,
Fangyi and I had an AR to describe what bad things can happen if IBIS
166.2 is approved in 7.0 and the Keysight BIRD with additional IR is
approved in IBIS 7.1.
I am enclosing a presentation which is a short review of the current IBIS
166.2, and adds a section demonstrating that no bad things will happen if
166.2 is included in IBIS 7.0 and the Keysight BIRD with additional IR is
approved in IBIS 7.1.
In summary:
- There are 81 possible flows based on IBIS 6.1 models.
- There are 625 possible flows in the Keysight BIRD.
- The 81 flows in IBIS 7.0 remain the same in IBIS 7.1.
Therefore the flows in IBIS 7.1 will not change any of the flows in IBIS
7.0.
Walter
Walter Katz
wkatz@xxxxxxxxxx
Phone 303.449-2308 <(303)%20449-2308>
Mobile 303.335-6156 <(303)%20335-6156>
