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DLL Enable/Disable
The DLL must be enabled for normal operation. DLL enable is required during power up
initialization, and upon returning to normal operation after having disabled the DLL for the
purpose of debug or evaluation. The DLL is automatically disabled when entering self
refresh operation and is automatically re-enabled upon exit of self refresh operation. Any
time the DLL is enabled, 200 clock cycles must occur to allow time for the internal clock to
lock to the externally applied clock before a Read command can be issued. This is the
reason for introducing timing parameter tXSRD for DDR SDRAM's (Exit Self Refresh to
Read Command). Non- Read commands can be issued 2 clocks after the DLL is enabled
via the EMRS command (tMRD) or 10 clocks after the DLL is enabled via self refresh exit
command (tXSNR, Exit Self Refresh to Non-Read Command).
Page 7-39
CONFIDENTIAL – DO NOT COPY
File No. SG-0212
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