[SI-LIST] DDR2 CMD/CTRL vs. CK Skew compensation problems

Hi all,
I am trying to design one DDR2 EVB board with one DIMM slot working at 
667Mbps. During the board routing, I am planing to keep CMD/CTRL lengh 
matching with clk signal as possible as I can. However, when I did 
pre-layout SI simulation for CMD/CTRL vs. CLK(assuming unbufferd DIMM Card 
F has been inserted into the slot), the timing analysis results show that 
the CMD signal at receiver pad side has much longer flight time than clk 
signal, and sometimes CMD  is even sampled at the next clk cycle instead of 
the corresponding clk cycle, which violates the read latency and write 
latency requirements. I checked the topology and found that in unbufferd 
DIMM card F, CMD trace lengh is almost 100mm longer than the CK trace. 
Based on my understandings, two ways may solve this problem. One is tuning 
silicon IO DLL timing,the other is extending the clk lengh on the EVB 
board. My question is:
1. How can I balance the two methods? Is there the third way to slove this 
problem?
2. In your unbufferd DIMM card mother board design, typically how much 
length difference between CMD and CLK signal group?
3. if the Register DIMM card instead unbuffered DIMM card insert into slot, 
what's the length match requirement in mother board design? Shall I need 
set my read and write latency one more cycle or EPROM in DIMM card has done 
it automatically?

Really appreciate your inputs.

fang

_________________________________________________________________
享用世界上最大的电子邮件系统― MSN Hotmail。 http://www.hotmail.com 

------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://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: