IBMN325164CT3
IBMN325804CT3
IBMN325404CT3
Preliminary
256Mb Synchronous DRAM - Die Revision B
Bank Activate Command
In relation to the operation of a fast page mode DRAM, the Bank Activate command correlates to a falling
RAS signal. The Bank Activate command is issued by holding CAS and WE high with CS and RAS low at the
rising edge of the clock. The Bank Select address BA0 - BA1 is used to select the desired bank. The row
address A0 - A12 is used to determine which row to activate in the selected bank. Activation of banks within
both decks of a 2-High stacked device is allowed.
The Bank Activate command must be applied before any Read or Write operation can be executed. The
delay from when the Bank Activate command is applied to when the first read or write operation can begin
must meet or exceed the RAS to CAS delay time (tRCD). Once a bank has been activated it must be pre-
charged before another Bank Activate command can be applied to the same bank. The minimum time inter-
val between successive Bank Activate commands to the same bank is determined by the RAS cycle time of
the device (tRC). The minimum time interval between interleaved Bank Activate commands (Bank A to Bank B
and vice versa) is the Bank to Bank delay time (t
). The maximum time that each bank can be held active
RRD
is specified as t
.
RAS(max)
Bank Activate Command Cycle
(CAS Latency = 3, tRCD = 3)
T0
T1
T2
T3
Tn
Tn+1
Tn+2
Tn+3
CK
. . . . . . . . . .
Bank A
Col. Addr.
Bank A
Row Addr.
Bank B
Row Addr.
Bank A
Row Addr.
. . . . . . . . . .
ADDRESS
RAS-CAS delay (tRCD
)
RAS - RAS delay time (tRRD
)
Write A
with Auto
Precharge
Bank B
NOP
Bank A
Activate
Bank A
Activate
. . . . . . . . . .
NOP
NOP
NOP
COMMAND
Activate
: “H” or “L”
RAS Cycle time (tRC
)
Bank Select
The Bank Select inputs, BA0 and BA1, determine the bank to be used during a Bank Activate, Precharge,
Read, or Write operation.
Bank Selection Bits
BA0
0
BA1
0
Bank
Bank 0
Bank 1
Bank 2
Bank 3
1
0
0
1
1
1
©IBM Corporation. All rights reserved.
Use is further subject to the provisions at the end of this document.
06K0608.F39375A
10/00
Page 9 of 66
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