64Mb: x32 SDRAM
AUTO REFRESH Operation
AUTO REFRESH Operation
The AUTO REFRESH command is used during normal operation of the device to refresh
the contents of the array. This command is nonpersistent, so it must be issued each
time a refresh is required. All active banks must be precharged prior to issuing an AUTO
REFRESH command. The AUTO REFRESH command should not be issued until the
minimum
t
RP is met following the PRECHARGE command. Addressing is generated by
the internal refresh controller. This makes the address bits “Don’t Care” during an AU-
TO REFRESH command.
After the AUTO REFRESH command is initiated, it must not be interrupted by any exe-
cutable command until
t
RFC has been met. During
t
RFC time, COMMAND INHIBIT or
NOP commands must be issued on each positive edge of the clock. The SDRAM re-
quires that every row be refreshed each
t
REF period. Providing a distributed AUTO RE-
FRESH command—calculated by dividing the refresh period (
t
REF) by the number of
rows to be refreshed—meets the timing requirement and ensures that each row is re-
freshed. Alternatively, to satisfy the refresh requirement a burst refresh can be employed
after every
t
REF period by issuing consecutive AUTO REFRESH commands for the num-
ber of rows to be refreshed at the minimum cycle rate (
t
RFC).
PDF: 09005aef811ce1fe
64mb_x32_sdram.pdf - Rev. T 04/13 EN
73
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