2Gb: x16, x32 Mobile LPDDR2 SDRAM S4
PRECHARGE Command
Figure 47: Write Data Mask – Second Data Bit Masked
CK#
CK
t WR
WL = 2
t WTR
CMD
Case 1: t DQSSmin
DQS
DQS#
DQ
DM
Case 2: t DQSSmax
DQS#
DQS
DQ
WRITE
t DQSSmin
D OUT 0 D OUT 1 D OUT 2 D OUT 3
t DQSSmax
D OUT 0 D OUT 1 D OUT 2 D OUT 3
DM
Don’t Care
Note:
1. For the data mask function, WL = 2, BL = 4 is shown; the second data bit is masked.
PRECHARGE Command
The PRECHARGE command is used to precharge or close a bank that has been activa-
ted. The PRECHARGE command is initiated with CS# LOW, CA0 HIGH, CA1 HIGH, CA2
LOW, and CA3 HIGH at the rising edge of the clock. The PRECHARGE command can be
used to precharge each bank independently or all banks simultaneously. For 4-bank de-
vices, the AB flag and bank address bits BA0 and BA1 are used to determine which
bank(s) to precharge. For 8-bank devices, the AB flag and the bank address bits BA0,
BA1, and BA2 are used to determine which bank(s) to precharge. The precharged
bank(s) will be available for subsequent row access t RPab after an all bank PRECHARGE
command is issued, or t RPpb after a single-bank PRECHARGE command is issued.
To ensure that 8-bank devices can meet the instantaneous current demand required to
operate, the row precharge time ( t RP) for an all bank PRECHARGE in 8-bank devices
( t RPab) will be longer than the row precharge time for a single-bank PRECHARGE
( t RPpb). For 4-bank devices, t RPab is equal to t RPpb.
ACTIVATE to PRECHARGE timing is shown in ACTIVATE Command (page 54).
PDF: 09005aef83f3f2eb
2gb_mobile_lpddr2_s4_g69a.pdf – Rev. N 3/12 EN
68
Micron Technology, Inc. reserves the right to change products or specifications without notice.
2010 Micron Technology, Inc. All rights reserved.
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