ESMT
M13S64164A
Auto Refresh & Self Refresh
Auto Refresh
An auto refresh command is issued by having CS , RAS and CAS held low with CKE and WE high at the rising edge of
the clock(CLK). All banks must be precharged and idle for tRP(min) before the auto refresh command is applied. No control of the
external address pins is requires once this cycle has started because of the internal address counter. When the refresh cycle has
completed, all banks will be in the idle state. A delay between the auto refresh command and the next activate command or
subsequent auto refresh command must be greater than or equal to the tRFC(min).
A maximum of eight consecutive AUTO REFRSH commands (with tRFC(min)) can be posted to any given SDRAM, and the
maximum absolute interval between any AUTO REFRESH command and the next AUTO REFRESH command is 8x15.6μm.
C L K
C L K
Auto
Refresh
C O M M A N D
PR E
C M D
CK E
= Hi gh
t R F C
t R P
Self Refresh
A self refresh command is defines by having CS , RAS , CAS and CKE held low with WE high at the rising edge of the
clock (CLK). Once the self refresh command is initiated, CKE must be held low to keep the device in self refresh mode. During the
self refresh operation, all inputs except CKE are ignored. The clock is internally disabled during self refresh operation to reduce
power consumption. The self refresh is exited by supplying stable clock input before returning CKE high, asserting deselect or NOP
command and then asserting CKE high for longer than tXSRD for locking of DLL.
C L K
C L K
Self
Refresh
Auto
Refresh
Rea d
C O M M A N D
CK E
t X S N R
t X S R
D
Note: After self refresh exit, input an auto refresh command immediately.
Elite Semiconductor Memory Technology Inc.
Publication Date : Jun. 2009
Revision : 1.4 24/48
ESMT [ ELITE SEMICONDUCTOR MEMORY TECHNOLOGY INC. ]
