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Altera_Forum's avatar
Altera_Forum
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14 years ago

ddr2 io standard

1. Are all the pins of ddr2 SSTL-18 or just DQ,DQS pins? If I config the DQ and DQS pins as SSTL-18 and others 2.5V.Does it work? 2. SSTL-18 Class I and SSTL-18 Class II are both ok,ri...
Altera_Forum's avatar
Altera_Forum
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14 years ago

All DDR2 control lines (address,# RAS,# CAS,# WE etc.) are specified to use a voltage referenced IO standard with termination resistors. It's a different question, if it's possible to drive the pins e.g. with 1.8V CMOS, but clearly not 2.5V. In any case, it would be outside specified operation.

Using single or dual terminated SSTL is matter of signal quality and connection length. Class I is mostly used for FPGA DDR interfaces.