Refresh Mode, Refresh Command | Texas Instruments TMS320C642x DSP

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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]

SPRUEM4A–November 2007

DDR2 Memory Controller

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Texas Instruments TMS320C642x DSP manual Refresh Mode, Refresh Command

Contents

Users Guide Submit Documentation Feedback Contents List of Figures List of Tables Read This First Purpose of the Peripheral Features Supported Use Case Statement Functional Block DiagramIndustry Standards Compliance Statement Clock Source Clock Control PLLC2 Configuration Clock ConfigurationMemory Map 3 DDR2 Memory Controller Internal Clock Domains DDR2 Memory Controller Signal Descriptions Signal DescriptionsClock enable Active high Pin Type Description Truth Table for DDR2 Sdram Commands DDR2 Sdram CommandsCommand Function Protocol Descriptions Refresh Command Refresh Mode Deactivation Dcab and Deac Dcab Command Deac Command Activation Actv Actv Command DDR2 Read Command Read Command DDR2 WRT Command Write WRT Command DDR2 MRS and Emrs Command Mode Register Set MRS and Emrs Addressable Memory Ranges Memory Width and Byte Alignment Bit External Memory Endianness Support Address 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 Sdram Logical Address-to-DDR2 Sdram Address Map DDR2 Sdram Column, Row, and Bank Access DDR2 Memory Controller Fifo Description DDR2 Memory Controller Interface Command Ordering and Scheduling, Advanced Concept Possible Race Condition Command Starvation Refresh Scheduling Self-Refresh ModeRefresh Urgency Levels Urgency Level Description Reset Sources Reset ConsiderationsReset Signal Reset Source Auto-Initialization Sequence VTP IO Buffer Calibration DDR2 Sdram Configuration by EMRS1 Command DDR2 Sdram Configuration by MRS CommandInitializing Configuration Registers DDR2 Memory Controller Peripheral Architecture Interrupt Support Power ManagementDMA Event Support Emulation Considerations Supported Use Cases Connecting the DDR2 Memory Controller to DDR2 Memory Connecting 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 Specification Sdram Timing Register Sdtimr Configuration Configuring Sdram Timing Registers Sdtimr and SDTIMR2Sdram Timing Register 2 SDTIMR2 Configuration DDR2 Data Register Field Manual Data Manual Formula DDR PHY Control Register Ddrphycr Configuration Configuring DDR PHY Control Register DdrphycrRegister Field Name Description D31-0 Mode D63-32Acronym Register Description DDR VTP Register Sdram Status Register Sdrstat Field Descriptions Sdram Status Register SdrstatBit Field Sdram 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 Sdrcr Sdram Timing Register Sdtimr Field Descriptions Sdram Timing Register Sdtimr Sdram Timing Register 2 SDTIMR2 Field Descriptions Sdram Timing Register 2 SDTIMR2 Peripheral Bus Burst Priority Register Pbbpr Peripheral Bus Burst Priority Register Pbbpr Interrupt Raw Register IRR Field Descriptions Interrupt Raw Register IRR Interrupt Masked Register IMR Field Descriptions Interrupt Masked Register IMR Interrupt Mask Set Register Imsr Field Descriptions Interrupt Mask Set Register Imsr Interrupt Mask Clear Register Imcr Field Descriptions Interrupt Mask Clear Register Imcr DDR PHY Control Register Ddrphycr Field Descriptions DDR PHY Control Register Ddrphycr VTP IO Control Register Vtpiocr Field Descriptions VTP IO Control Register Vtpiocr DDR VTP Enable Register Ddrvtper Field Descriptions DDR VTP Enable Register DdrvtperDDR VTP Register Ddrvtpr DDR VTP Register Ddrvtpr Field Descriptions Additions/Modifications/Deletions Table A-1. Document Revision History Important Notice