1Gb: x4, x8, x16 DDR3 SDRAM
Commands
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 affec-
ted.
ZQ CALIBRATION LONG
The ZQ CALIBRATION LONG (ZQCL) command is used to perform the initial calibra-
tion during a power-up initialization and reset sequence (see Figure 5± (page 135)).
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 en-
gine 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
a 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 satis-
fied.
ZQ CALIBRATION SHORT
The ZQ CALIBRATION SHORT (ZQCS) command is used to perform periodic calibra-
tions to account for small voltage and temperature variations. A shorter timing window
is provided to perform the reduced calibration and transfer of values as defined by tim-
ing parameter tZQCS. A ZQCS command can effectively correct a minimum of ±.5ꢀ RON
and RTT impedance error within 64 clock cycles, assuming the maximum sensitivities
specified in Table 42 (page 66) and Table 43 (page 66).
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:±] inputs selects the bank, and the address
provided on inputs A[n:±] selects the row. This row remains open (or active) for accesses
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:±] 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 A1± determines whether auto precharge is used. If auto precharge is se-
lected, the row being accessed will be precharged at the end of the READ burst. If auto
PDF: 09005aef826aa906
1Gb_DDR3_SDRAM.pdf - Rev. L 03/13 EN
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