Texas Instruments TMS320DM643 manual Refresh Mode, Refresh Command

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Peripheral Architecture

2.4.1Refresh Mode

The DDR2 memory controller issues refresh commands to the DDR2 SDRAM memory (Figure 4). REFR is automatically preceded by a DCAB command, ensuring the deactivation of all CE spaces and banks selected. Following the DCAB command, the DDR2 memory controller begins performing refreshes at a rate defined by the refresh rate (RR) bit in the SDRAM refresh control register (SDRCR). Page information is always invalid before and after a REFR command; thus, a refresh cycle always forces a page miss. This type of refresh cycle is often called autorefresh. Autorefresh commands may not be disabled within the DDR2 memory controller. See Section 2.9 for more details on REFR command scheduling.

Figure 4. Refresh Command

DDR_CLK DDR_CLK

RFR

DDR_CKE

DDR_CS

DDR_RAS

DDR_CAS

DDR_WE

DDR_A[12:0]

DDR_BA[2:0]

DDR_DQM[3:0]

SPRU986B–November 2007

DDR2 Memory Controller

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Contents Users Guide Submit Documentation Feedback Contents List of Figures List of Tables Read This First Purpose of the Peripheral FeaturesSupported Use Case Statement Functional Block DiagramIndustry Standards Compliance Statement Clock Source Clock ControlPLLC2 Configuration Clock ConfigurationMemory Map 3 DDR2 Memory Controller Internal Clock DomainsDDR2 Memory Controller Signal Descriptions Signal DescriptionsClock enable Active high Pin Type DescriptionTruth Table for DDR2 Sdram Commands DDR2 Sdram CommandsCommand Function Protocol DescriptionsRefresh Command Refresh ModeDeactivation Dcab and Deac Dcab CommandDeac Command Activation Actv Actv CommandDDR2 Read Command Read CommandDDR2 WRT Command Write WRT CommandDDR2 MRS and Emrs Command Mode Register Set MRS and EmrsAddressable Memory Ranges Memory Width and Byte AlignmentBit External Memory Endianness ConsiderationsInternal Data 64-Bit DDRA21 DDRD150 Internal Data 64-Bit DDRA2 DDRD310Address Mapping Bank Configuration Register Fields for Address MappingBit Field Bit Value Bit Description Logical Address-to-DDR2 Sdram Address Map for 16-bit Sdram Logical Address-to-DDR2 Sdram Address Map for 32-Bit SdramLogical Address-to-DDR2 Sdram Address Map DDR2 Sdram Column, Row, and Bank Access DDR2 Memory Controller Fifo Description DDR2 Memory Controller InterfaceCommand Ordering and Scheduling, Advanced Concept Possible Race Condition Command StarvationRefresh Scheduling Self-Refresh ModeRefresh Urgency Levels Urgency Level DescriptionReset Sources Reset ConsiderationsReset Signal Reset Source Auto-Initialization Sequence VTP IO Buffer CalibrationDDR2 Sdram Configuration by EMRS1 Command DDR2 Sdram Configuration by MRS CommandInitializing Configuration Registers DDR2 Memory ControllerPeripheral Architecture Interrupt Support Power ManagementDMA Event Support Emulation Considerations Supported Use Cases Connecting the DDR2 Memory Controller to DDR2 MemoryConnecting DDR2 Memory Controller for 32-Bit Connection Sdram Bank Configuration Register Sdbcr Configuration Configuring Sdram Bank Configuration Register SdbcrConfiguring Sdram Refresh Control Register Sdrcr DDR2 Memory Refresh SpecificationSdram Timing Register Sdtimr Configuration Configuring Sdram Timing Registers Sdtimr and SDTIMR2Sdram Timing Register 2 SDTIMR2 Configuration DDR2 Data Register Field Manual Data Manual FormulaDDR PHY Control Register Ddrphycr Configuration Configuring DDR PHY Control Register DdrphycrRegister Field Name Description D63-32Sdram Status Register Sdrstat Field Descriptions Sdram Status Register SdrstatAcronym Register Description DDR VTP RegisterSdram Bank Configuration Register Sdbcr Field Descriptions Sdram Bank Configuration Register SdbcrBit Field Value Description Reserved Reserved. Always write a 0 to this bit Sdram Refresh Control Register Sdrcr Field Descriptions Sdram Refresh Control Register SdrcrSdram Timing Register Sdtimr Field Descriptions Sdram Timing Register SdtimrSdram Timing Register 2 SDTIMR2 Field Descriptions Sdram Timing Register 2 SDTIMR2Peripheral Bus Burst Priority Register Pbbpr Peripheral Bus Burst Priority Register PbbprInterrupt Raw Register IRR Field Descriptions Interrupt Raw Register IRRInterrupt Masked Register IMR Field Descriptions Interrupt Masked Register IMRInterrupt Mask Set Register Imsr Field Descriptions Interrupt Mask Set Register ImsrInterrupt Mask Clear Register Imcr Field Descriptions Interrupt Mask Clear Register ImcrDDR PHY Control Register Ddrphycr Field Descriptions DDR PHY Control Register DdrphycrVTP IO Control Register Vtpiocr Field Descriptions VTP IO Control Register VtpiocrDDR VTP Enable Register Ddrvtper Field Descriptions DDR VTP Enable Register DdrvtperDDR VTP Register Ddrvtpr DDR VTP Register Ddrvtpr Field DescriptionsAdditions/Modifications/Deletions Table A-1. Document Revision HistoryImportant Notice