Help me overcome problems with reading data from DDR IO

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neyee

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I design a ddr1 io in our chip, when I read data from memery with parallel terminations resistor the result is OK, the trace on pcb is about 6 inch(15cm),but
when I take off the parallel terminations resistance and only left the series resistor, I find I can't read right data from the memory chip, I think it is because of reflection, I want to know if I put the memory chip closer to our chip and only with series resistor, Can the ddr io work succesfully? How can simulation this?
thanks very much for your answer!!!
 

ddr io

for what you take off terminators?

if I put the memory chip closer to our chip and only with series resistor, Can the ddr io work succesfully...

50/50
because - long-transmission line, when (net length) >> (signal wave lengh),
and what tells specification of DDR about terminations?

look on attach, for example
 

Re: about DDR io design

Thank you very much , according to system cost so we need take off the parallel resistor
 

Re: about DDR io design

Thank you very much
 

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