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4.4SDRAMRefreshControlRegister(SDRFC)
DDR2MemoryControllerRegisters
TheSDRAMrefreshcontrolregister(SDRFC)isusedtoconfiguretheDDR2memorycontrollerto:
•EnterandExittheself-refreshstate.
•MeettherefreshrequirementoftheattachedDDR2devicebyprogrammingtherateatwhichthe
DDR2memorycontrollerissuesautorefreshcommands.
TheSDRFCisshowninFigure23anddescribedinTable21.
Figure23.SDRAMRefreshControlRegister(SDRFC)
31302916
SRRsvdReserved
R/W-R/W-R-0x0
0x00x0
150
REFRESH_RATE
R/W-0x753
LEGEND:R/W=Read/Write;R=Readonly;-n=valueafterreset
Table21.SDRAMRefreshControlRegister(SDRFC)FieldDescriptions
BitFieldValueDescription
31SRSelf-refreshbit.Writinga1tothisbitwillcauseconnectedSDRAMdevicestobeplaceintoSelf
RefreshmodeandtheDDR2MemoryControllertoentertheSelfRefreshstate.
0Exitself-refreshmode.
1Enterself-refreshmode.
30ReservedReserved.Writestothisregistermustkeepthisfieldatitsdefaultvalue.
29-16ReservedReserved.Thereservedbitlocationisalwaysreadas0.Avaluewrittentothisfieldhasnoeffect.
15-0REFRESH_RATERefreshratebits.ThevalueinthisfieldisusedtodefinetherateatwhichconnectedSDRAM
deviceswillberefreshedasfollows:effect.
SDRAMrefreshrate=DDR_CLKclockrate/REFRESH_RATE
Writingavaluelessthan0x0100tothisfieldwillcauseittobeloadedwith2*T_RFCvaluefrom
theSDRAMTiming1Register.
40DSPDDR2MemoryControllerSPRUEK5A–October2007
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