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Renesas Singapore - Knowledgebase

Does it need to pull up CS3#, Data Bus, RAS#, CAS# and others using SDRAM?

Latest Updated:09/28/2009


In the case of SDRAM usage, does it need to pull-up CS3#, Data Bus, RAS#, CAS# and other pins?


These pins will be INPUT ports at RESET release timing. But their level will be fixed to High or Low by the weak keeper circuit. If you want to fix a pin speciically to alevel (High or Low), you need to pull-up/pull-down the pin using the external circuit. For example, CS3# needs to be fixed to High level when it does not access SDRAM. It is recommended that this pin be pulled up using a 2k ohm register. Other pins are same. To prevent malfunction until the pin can be set, it is recommended that it also be pulled up/down as needed.
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