[SI-LIST] AW: Re: DDR-II: SSTL_18 & ODT
- From: hermann.ruckerbauer@xxxxxxxxxxxx
- To: dcs@xxxxxxxxxxxxxxxx, bstott@xxxxxxxxxxxxxxxx
- Date: Tue, 20 Aug 2002 07:50:56 +0200
Hi D.C.,=20
I do not really aggree with the comment that=20
"ODT is still somewhat controversial, which is why there are provisions =
to disable it altogether."
There are situations, where you will use ODT to ensure SI (e. g. =
Desktop PC system with 2 or 3 Slots @533 ot 666 Mb/s),=20
and there will be implementations, where it may be not necessary to use =
ODT (e. g. P2P systems).
And for this case it is possible to switch off ODT, to save the Power.
And this was the reason to have a "off" setting for ODT too.
JEDEC is not defining how you have to implement a system, it is only =
defining the features, and giving
a possible way to do the job. So, it is totally up to you, how you get =
the system running with the
available features.
regards
Hermann
-----Urspr=FCngliche Nachricht-----
Von: D. C. Sessions [mailto:dcs@xxxxxxxxxxxxxxxx]
Gesendet am: Montag, 19. August 2002 18:31
An: bstott@xxxxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: DDR-II: SSTL_18 & ODT
On Mon, 2002-08-12 at 11:35, Bret Stott wrote:
> I am a new member of this list and I have a few questions about =
DDR-II that I=20
> was hoping someone could help me out with. Currently, I don't have =
access to=20
> JEDEC so most of my information is from alternate sources such as the =
Samsung=20
> DDR-II spec.
>=20
> o Can anyone point me at a SSTL_18 specification?
Yes, but then I'd have to kill you.
Seriously, this should be hitting publication Very Soon Now.
We just recently gave the JEDEC office the go-ahead. Look
for JESD8-15.
> o Can someone help me understand the on-die-termination strategy for =
DDR-II? =20
> Why are the values 75 & 150 Ohms? What electrical topology is being =
assumed?
Your basic DDR DRAM topology, w/o the motherboard shunt resistors.
ODT is still somewhat controversial, which is why there are
provisions to disable it altogether.
> o My initial analysis suggests that it is possible to use class I =
drivers for=20
> the address bus (5 load) and also for a point-to-point data bus. The =
data bus=20
> may require some non-standard termination values though. Does anyone =
have any=20
> information that supports of refutes this?
There Is No Class One. SSTL-18 ditches the "Class I" driver
spec since the SSTL-2 class I spec has caused a lot of
confusion and we couldn't find any valid uses for it.
(Yeah, I know that that last if flame bait. If you don't like
the JC-16 tendency to concentrate on DRAM to the exclusion of
other applications, JOIN THE FREAKING COMMITTEE!)
--=20
| May I have the serenity to accept the things I cannot change, |
| the strength to change the things I cannot accept, and the |
| cunning to hide the bodies of those who got in my way. |
+------------- D. C. Sessions <dcs@xxxxxxxxxxxxxxxx> -----------+
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at: =20
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages=20
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
