Editing Synchronous dynamic random-access memory (section)

== Auto refresh ==
It is possible to refresh a RAM chip by opening and closing (activating and precharging) each row in each bank. However, to simplify the memory controller, SDRAM chips support an "auto refresh" command, which performs these operations to one row in each bank simultaneously. The SDRAM also maintains an internal counter, which iterates over all possible rows. The memory controller must simply issue a sufficient number of auto refresh commands (one per row, 8192 in the example we have been using) every refresh interval (t<sub>REF</sub> = 64 ms is a common value). All banks must be idle (closed, precharged) when this command is issued.