W982516BH Datasheet, PDF (16/43 Pages) Winbond – 4M X 4 BANKS X 16 BIT SDRAM

W982516BH
The Power-down mode is exited by bringing CKE high. When CKE goes high, a No Operation
Command is required on the next rising clock edge, depending on t_CK. The input buffers need to be
enabled with CKE held high for a period equal to t_CKS (min) + t_CK (min).
No Operation Command
The No Operation Command should be used in cases when the SDRAM is in a idle or a wait state to
prevent the SDRAM from registering any unwanted commands between operations. A No Operation
Command is registered when CS is low with RAS, CAS, and WE held high at the rising edge of the
clock. A No Operation Command will not terminate a previous operation that is still executing, such as
a burst read or write cycle.
Deselect Command
The Deselect Command performs the same function as a No Operation Command. Deselect
Command occurs when CS is brought high, the RAS, CAS, and WE signals become don't cares.
Clock Suspend Mode
During normal access mode, CKE must be held high enabling the clock. When CKE is registered low
while at least one of the banks is active, Clock Suspend Mode is entered. The Clock Suspend mode
deactivates the internal clock and suspends any clocked operation that was currently being executed.
There is a one clock delay between the registration of CKE low and the time at which the SDRAM
operation suspends. While in Clock Suspend mode, the SDRAM ignores any new commands that are
issued. The Clock Suspend mode is exited by bringing CKE high. There is a one clock cycle delay
from when CKE returns high to when Clock Suspend mode is exited.
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