48SD1616
256Mb (4-Meg X 16-Bit X 4-Banks) SDRAM
CKE Truth Table
CURRENT STATE
COMMAND
N-1
N
CS
RAS
CAS
WE
ADDRESS
Active
Clock suspended mode entry
Clock Suspend
H
L
L
H
H
H
H
L
L
L
L
L
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Any
Clock Suspend
Clock Suspend mode exit
Auto-refresh command (REF)
Self-refresh entry (SELF)
H
H
L
x
x
x
x
Idle
Idle
Idle
L
L
L
H
x
L
L
H
x
H
H
H
x
L
L
L
Power down entry
L
HL
L
Self Refresh
Power down
Self Refresh exit (SELFX)
H
H
H
H
H
x
H
H
x
H
H
x
L
Power down exit
H
Note: H:V L:V x V or V
IL
IH
IL
IH
Clock suspend mode entry: The SDRAM enters clock suspend mode from active mode by setting CKE to
Low. If a command is input in the clock suspend mode entry cycle, the command is valid. The clock suspend
mode change depending on the current status (1 clock before) as described below.
ACTIVE clock suspend: This suspend mode ignores inputs after the next clock by internally maintaining
the bank active status.
READ suspend and READ with Auto-precharge suspend: The data being output is held ( and continues
to be output).
WRITE suspend and WRIT with Auto-precharge suspended: In this mode, external signals are not
accepted. However, the internal state is held.
Clock suspend: During clock suspend mode, keep the CKE to Low.
Clock suspend mode exit: The SDRAM exits from clock suspend mode by setting CKE to High during the
clock suspend state.
IDLE: In this state, all banks are not selected, and have completed precharge operation.
Auto-refresh command (REF): When this command is input from the IDLE state, the SDRAM starts auto-
refresh operation. (The auto-refresh is the same as the CBR refresh of conventional DRAMs.) During the
auto-refresh operation, refresh address and bank select address are generated inside the SDRAM. For
every auto-refresh cycle, the internal address counter is updated. Accordingly, 8192 cycles are required to
refresh the entire memory contents. Before executing the auto-refresh command, all the banks must be in
01.07.05 REV 4
All data sheets are subject to change without notice 11
©2005 Maxwell Technologies
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MAXWELL [ MAXWELL TECHNOLOGIES ]
