![](http://datasheet.mmic.net.cn/200000/MT41J128M16HA-107-D_datasheet_15084792/MT41J128M16HA-107-D_115.png)
Commands
DESELECT
The DESELT (DES) command (CS# HIGH) prevents new commands from being execu-
ted by the DRAM. Operations already in progress are not affected.
NO OPERATION
The NO OPERATION (NOP) command (CS# LOW) prevents unwanted commands from
being registered during idle or wait states. Operations already in progress are not affected.
ZQ CALIBRATION LONG
The ZQ CALIBRATION LONG (ZQCL) command is used to perform the initial calibra-
This command may be issued at any time by the controller depending on the system
environment. The ZQCL command triggers the calibration engine inside the DRAM. Af-
ter calibration is achieved, the calibrated values are transferred from the calibration
engine to the DRAM I/O, which are reflected as updated RON and ODT values.
The DRAM is allowed a timing window defined by either tZQinit or tZQoper to perform
the full calibration and transfer of values. When ZQCL is issued during the initialization
sequence, the timing parameter tZQinit must be satisfied. When initialization is com-
plete, subsequent ZQCL commands require the timing parameter tZQoper to be satisfied.
ZQ CALIBRATION SHORT
The ZQ CALIBRATION SHORT (ZQCS) command is used to perform periodic calibra-
tions to account for small voltage and temperature variations. The shorter timing
window is provided to perform the reduced calibration and transfer of values as defined
by timing parameter tZQCS. A ZQCS command can effectively correct a minimum of
0.5% RON and RTT impedance error within 64 clock cycles, assuming the maximum sen-
ACTIVATE
The ACTIVATE command is used to open (or activate) a row in a particular bank for a
subsequent access. The value on the BA[2:0] inputs selects the bank, and the address
provided on inputs A[n:0] selects the row. This row remains open (or active) for access-
es until a PRECHARGE command is issued to that bank.
A PRECHARGE command must be issued before opening a different row in the same bank.
READ
The READ command is used to initiate a burst read access to an active row. The address
provided on inputs A[2:0] selects the starting column address depending on the burst
length and burst type selected (see Burst Order table for additional information). The
value on input A10 determines whether or not auto precharge is used. If auto precharge
is selected, the row being accessed will be precharged at the end of the READ burst. If
auto precharge is not selected, the row will remain open for subsequent accesses. The
value on input A12 (if enabled in the mode register) when the READ command is issued
2Gb: x4, x8, x16 DDR3 SDRAM
Commands
PDF: 09005aef826aaadc
2Gb_DDR3_SDRAM.pdf – Rev. K 04/10 EN
115
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