is43lr16800f-6bl Integrated Silicon Solution, Inc., is43lr16800f-6bl Datasheet - Page 38

• Manufacturer Part Number: is43lr16800f-6bl
• Description: 2m X 16bits X 4banks Mobile Ddr Sdram
• Manufacturer: Integrated Silicon Solution, Inc.

Rev. 00A | Dec. 2010
Auto refresh
is required. The refresh addressing is generated by the internal refresh controller. The Mobile DDR requires AUTO REFRESH commands at an
average periodic interval of tREFI. To allow for improved efficiency in scheduling and switching between tasks, some flexibility in the
absolute refresh interval is provided. A maximum of eight AUTO REFRESH commands can be posted to any given Mobile DDR, and the
maximum absolute interval between any AUTO REFRESH command and the next AUTO REFRESH command is 8*tREFI.
Figure33 : Auto refresh
Self refresh
interval timing while in Self Refresh mode is scheduled internally in the Mobile DDR and may vary and may not meet tREFI time. "Don't
Care" except CKE, which must remain low. An internal refresh cycle is scheduled on Self Refresh entry. The procedure for exiting Self
Refresh mode requires a series of commands. First clock must be stable before CKE going high. NOP commands should be issued for the
duration of the refresh exit time (tXSR), because time is required for the completion of any internal refresh in progress. The use of SELF
REFRESH mode introduces the possibility that an internally timed event can be missed when CKE is raised for exit from self refresh mode.
Figure34 : Self refresh
The Auto refresh command is used during normal operation of the Mobile DDR. It is non persistent, so must be issued each time a refresh
This state retains data in the Mobile DDR, even if the rest of the system is powered down (even without external clocking). Note refresh
DQS, DQ, DM
A0~A9, A11
Command
DQS , DQ, DM
BA 0, BA 1
Command
/CLK
CLK
CKE
A10
Address
/CLK
CLK
CKE
tIS
tIS
NOP
T0
tIH
tIH
tIS
tIS
Don’t care
NOP
T0
tRP
tIH
tIH
One Bank
Self-refresh mode entry
All Banks
PCG
T1
BA
tIS
AREF
tCK
T1
VALID
NOP
T2
tCH
tRP
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tCL
NOP
T3
Don’t care
Ta 0
AREF
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T4
Self-refresh mode exit
tIS
NOP
NOP
tRFC
Ta1
Ta0
AREF
tXSR
Tb0
VALID
NOP
VALID
VALID
Tb0
IS43/46LR16800F
tRFC
Advanced Information
NOP
Ta2
ACT
RA
RA
BA
Tb0
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