[SI-LIST] Re: DDR-1 termination (short point-to-point)
- From: "Novak David (TTE)" <david.novak@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 4 Feb 2005 13:45:37 -0500
Yes, but most memory controllers spec. a 300mV(max) for 'shoots.
The interesting question here is how real is that 300mV spec? If the DDR
can handle more, why can't the memory controller?
David=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Landrum, Chris
Sent: Friday, February 04, 2005 12:03 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR-1 termination (short point-to-point)
Doesn't DDR1 allow for overshoot/undershoot up to 1.5V as long as it is
for a short period of time (500pS or so)?=3D20
-Chris
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Novak David (TTE)
Sent: Friday, February 04, 2005 10:18 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDR-1 termination (short point-to-point)
The DDR will never be a "slow drive". However, the x32 GDDR parts do
allow more control over drive strength.
As long as you keep the lines short, you should have no problems with a
simple series resistor in each line. This is a very common termination
scheme for point-to-point DDR designs.
If it were not for the 300mV overshoot specs. on most DDR memory
controllers, you wouldn't even need the series resistors.
David
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Anders Frederiksen
Sent: Thursday, February 03, 2005 5:00 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] DDR-1 termination (short point-to-point)
I'm connecting a lot of DDR1 ram to a FPGA (Virtex2pro). Common schemes
recommended is "embedding a DIMM design" (which would be plain stupid
imho) and doing a full parallel termination in both ends (typically in
0402). The latter is naturally sensible - but it occurs to be kind of a
overkill for ponit-to-point lines of "only" 5cm (~2") or less. Has
anyone experience with simpler termination schemes? I mean for standard
busses one would rely on slow drivers only...
Cheers,
Anders
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