97SD3240 Datasheet, PDF (11/39 Pages) Maxwell Technologies – 1.25Gb SDRAM 8-Meg X 40-Bit X 4-Banks

1.25Gb (8-Meg X 40-Bit X 4-Banks) SDRAM
97SD3240
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
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.
Self Refresh entry (SELF)¹: When this command is input during the IDLE state, the SDRAM starts self-
refresh operation. After the execution of this command, self-refresh continues while CKE is Low. Since self-
refresh is performed internally and automatically, external refresh operations are unnecessary.
Power down mode entry: When this command is executed during the IDLE state, the SDRAM enters
power down mode. In power down mode, power consumption is suppresses by cutting off the initial input
circuit.
Self-refresh exit: When this command is executed during self-refresh mode, the SDRAM can exit from self-
refresh mode. After exiting from self-refresh mode, the SDRAM enters the IDLE state.
Power down exit: When this command is executed at power down mode, the SDRAM can exit from power
down mode. After exiting from power down mode, the SDRAM enters the IDLE state.
1. Self refresh mode should only be used at temperatures below 70°C.
02.04.05 Rev 3
All data sheets are subject to change without notice 11
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