HM5225165B/HM5225805B/HM5225405B-75/A6/B6
CKE Truth Table
CKE
Current state
Command
n - 1
H
L
n
L
CS
×
RAS CAS WE Address
Active
Clock suspend mode entry
Clock suspend
×
×
×
L
L
H
×
H
×
H
×
×
×
×
L
L
H
×
H
×
H
×
×
×
×
×
×
×
×
×
×
×
×
×
Any
L
×
×
Clock suspend
Clock suspend mode exit
Auto-refresh command (REF)
Self-refresh entry (SELF)
Power down entry
L
H
H
L
×
×
Idle
Idle
Idle
H
H
H
H
L
L
H
H
H
×
L
L
L
L
H
L
Self refresh
Power down
Self refresh exit (SELFX)
Power down exit
H
H
H
H
H
×
L
H
L
L
H
×
L
H
Note: H: VIH. L: VIL. ×: VIH or VIL.
Clock suspend mode entry: The SDRAM enters clock suspend mode from active mode by setting CKE to
Low. If command is input in the clock suspend mode entry cycle, the command is valid. The clock suspend
mode changes depending on the current status (1 clock before) as shown 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 suspend: 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 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 times are required to refresh
the entire memory. Before executing the auto-refresh command, all the banks must be in the IDLE state. In
addition, since the precharge for all banks is automatically performed after auto-refresh, no precharge
command is required after auto-refresh.
Data Sheet E0082H10
13
ELPIDA [ ELPIDA MEMORY ]
