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4.6SDRAMTiming2Register(SDTIM2)
DDR2MemoryControllerRegisters
LiketheSDRAMtiming1register(SDTIM1),theSDRAMtiming2register(SDTIM2)alsoconfiguresthe
DDR2memorycontrollertomeettheACtimingspecificationoftheDDR2memory.SeetheDDR2
memorydatasheetforinformationontheappropriatevaluestoprogrameachfield.Thebitfieldsinthe
SDTIM2registerareonlywriteablewhentheTIMUNLOCKbitoftheSDRAMConfigurationregister
(SDCFG)isunlocked.SDTIM2isshowninFigure25anddescribedinTable23.
Figure25.SDRAMTiming2Register(SDTIM2)
312524232216
ReservedT_ODTT_SXNR
R-0x0R/W-0x3R/W-0x7F
1587540
T_SXRDT_RTPT_CKE
R/W-0xFFR/W-0x7R/W-0x1F
LEGEND:R/W=Read/Write;R=Readonly;-n=valueafterreset;-x=valueisindeterminateafterreset;
Table23.SDRAMTiming2Register(SDTIM2)FieldDescriptions
BitFieldValueDescription
31-25ReservedReserved.Thereservedbitlocationisalwaysreadas0.Avaluewrittentothisfieldhasnoeffect.
24-23T_ODTThesebitsspecifythenumberofDDR_CLKcyclesfromODTenabletowritedatadrivenforDDR2
SDRAM.T_ODTmustbelessthantheCASlatencyminusone.Calculateusingthisformula:
T_ODT=CASlatency-t
aond
-1
22-16T_SXNR0-7FhThesebitsspecifytheminimumnumberofDDR_CLKcyclesfromaself_refreshexittoanyother
commandexceptareadcommand,minus1.Thevalueforthesebitscanbederivedfromthet
SXNR
ACtimingparameterintheDDR2datasheet.Calculateusingthisformula:
T_SXNR=(t
SXNR
/DDR_CLK)-1
15-8T_SXRD0-FFhThesebitsspecifytheminimumnumberofDDR_CLKcyclesfromaself_refreshexittoaread
command,minus1.Thevalueforthesebitscanbederivedfromthet
SXRD
ACtimingparameterin
theDDR2datasheet.Calculateusingthisformula:
T_SXRD=t
SXRD
-1
7-5T_RTP0-7hThesebitsspecifytheminimumnumberofDDR_CLKcyclesfromalastreadcommandtoa
prechargecommand,minus1.Thevalueforthesebitscanbederivedfromthet
rtp
ACtiming
parameterintheDDR2datasheet.Calculateusingthisformula:
T_RTP=(t
rtp
/DDR_CLK)-1
4-0T_CKE0-1FhThesebitsspecifytheminimumnumberofDDR_CLKcyclesbetweentransitionsontheDDR_CKE
pin,minus1.Thevalueforthesebitscanbederivedfromthet
cke
ACtimingparameterinthe
DDR2datasheet.Calculateusingthisformula:
T_CKE=t
cke
-1
SPRUEK5A–October2007DSPDDR2MemoryController43
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