Datasheet

SM646UDR26485-2-I
January 31, 2006
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13
Extended Mode Register Table Definition
The extended mode register controls functions beyond those controlled by the mode register; these additional functions are DLL
enable/ disable, output drive strength, ODT (R
TT
), Posted CAS additive latency (AL), off-chip driver impedance calibration
(OCD), DQS# enable/disable, RDQS/RDQS# enable/disable, and OUTPUT enable/disable. The extended mode register is
programmed via the LOAD MODE (LM) command and will retain the stored information until it is programmed again or the
device loses power. Reprogramming the extended mode register will not alter the contents of the memory array, provided it is
performed correctly.
The extended mode register must be loaded when all banks are idle and no bursts are in progress, and the controller must wait
the specified time t
MRD
before initiating any subsequent operation. Violating either of these requirements could result in
unspecified operation.
Notes:
1. BA2 and A14~A15 are reserved for future use and must be programmed to 0 when setting the mode register.
2. When the adjust mode of the OCD Calibration Program is issued, AL from previously set value must be applied.
3. After setting the OCD Calibration Program to default, OCD mode needs to be exited by setting A9-A7 to 000.
4. Outputs disabled - DQs, DQSs, DQS#s, RDQSs, RDQS#s. This feature is used in conjunction with DIMM I
DD
measurements when I
DDQ
is not desired to be included.
5. If RDQS is enabled, the DM function is disabled. RDQS is active for reads and don’t care for writes.