sdram autorefresh ??

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   self refresh the row address is increment by internal oscillator.
    so
    1- in auto refresh the row address is increment by internal oscillator or my external clock in ?
    2- in auto refresh row address increment internal automatically counter or i change row address by external command?
    3- auto refresh need minimum time or minimum clock cycle to end
    because i find in data sheet it need minimum time not minimum clock cycle ?

    4- precharge command can use it instead of auto refresh. if i will not use all sdram size capacity . to refresh some little row in bank

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are there problem in my question it is not clear ?