IBMN625404GT3B
IBMN625804GT3B
Preliminary
256Mb Double Data Rate Synchronous DRAM
Operations
Bank/Row Activation
Before any Read or Write commands can be issued to a bank within the DDR SDRAM, a row in that bank
must be “opened” (activated). This is accomplished via the Active command and addresses A0-A12, BA0 and
BA1 (see Activating a Specific Row in a Specific Bank), which decode and select both the bank and the row
to be activated. After opening a row (issuing an Active command), a Read or Write command may be issued
to that row, subject to the t
specification. A subsequent Active command to a different row in the same
RCD
bank can only be issued after the previous active row has been “closed” (precharged). The minimum time
interval between successive Active commands to the same bank is defined by t . A subsequent Active com-
RC
mand to another bank can be issued while the first bank is being accessed, which results in a reduction of
total row-access overhead. The minimum time interval between successive Active commands to different
banks is defined by t
.
RRD
Activating a Specific Row in a Specific Bank
CK
CK
HIGH
CKE
CS
RAS
CAS
WE
RA = row address.
BA = bank address.
RA
BA
A0-A12
BA0, BA1
Don’t Care
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