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2Gb: x16, x32 Mobile LPDDR2 SDRAM S4
ACTIVATE Command
ACTIVATE Command
The ACTIVATE command is issued by holding CS# LOW, CA0 LOW, and CA1 HIGH at the
rising edge of the clock. The bank addresses BA[2:0] are used to select the desired bank.
Row addresses are used to determine which row to activate in the selected bank. The
ACTIVATE command must be applied before any READ or WRITE operation can be exe-
cuted. The device can accept a READ or WRITE command at t RCD after the ACTIVATE
command is issued. After a bank has been activated, it must be precharged before an-
other ACTIVATE command can be applied to the same bank. The bank active and pre-
charge times are defined as t RAS and t RP, respectively. The minimum time interval be-
tween successive ACTIVATE commands to the same bank is determined by the RAS cy-
cle time of the device ( t RC). The minimum time interval between ACTIVATE commands
to different banks is t RRD.
Figure 27: ACTIVATE Command
T0
T1
T2
T3
Tn
Tn+1
Tn+2
Tn+3
CK#
CK
CA[9:0]
Bankn
row addr
Row addr
Bankm
row addr
Row addr
Bankn
col addr
Col addr
Bankn
Bankn
row addr
Row addr
t RRD
t RCD
t RAS
t RC
t RP
CMD
ACTIVATE
NOP
ACTIVATE
READ
PRECHARGE
NOP
NOP
ACTIVATE
Notes:
1. t RCD = 3, t RP = 3, t RRD = 2.
2. A PRECHARGE ALL command uses t RPab timing, and a single-bank PRECHARGE com-
mand uses t RPpb timing. In this figure, t RP is used to denote either an all-bank PRE-
CHARGE or a single-bank PRECHARGE.
8-Bank Device Operation
Two rules regarding 8-bank device operation must be observed. One rule restricts the
number of sequential ACTIVATE commands that can be issued; the second provides ad-
ditional RAS precharge time for a PRECHARGE ALL command.
The 8-Bank Device Sequential Bank Activation Restriction: No more than four banks
can be activated (or refreshed, in the case of REFpb) in a rolling t FAW window. To con-
vert to clocks, divide t FAW[ns] by t CK[ns], and round up to the next integer value. For
example, if RU( t FAW/ t CK) is 10 clocks, and an ACTIVATE command is issued in clock n ,
no more than three further ACTIVATE commands can be issued at or between clock
n + 1 and n + 9. REFpb also counts as bank activation for purposes of t FAW.
The 8-Bank Device PRECHARGE ALL Provision: t RP for a PRECHARGE ALL command
must equal t RPab, which is greater than t RPpb.
PDF: 09005aef83f3f2eb
2gb_mobile_lpddr2_s4_g69a.pdf – Rev. N 3/12 EN
54
Micron Technology, Inc. reserves the right to change products or specifications without notice.
2010 Micron Technology, Inc. All rights reserved.
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