Texas Instruments TMS320C6452 DSP manual Memory Width and Byte Alignment, Write WRT Command

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Peripheral Architecture

2.4.6Write (WRT) Command

Prior to a WRT command, the desired bank and row are activated by the ACTV command. Following the WRT command, a write latency is incurred. Write latency is equal to CAS latency minus 1. All writes have a burst length of 8. The use of the DDR_DQM outputs allows byte and halfword writes to be executed.

Figure 9 shows the timing for a write on the DDR2 memory controller.

If the transfer request is for less than 8 words, depending on the scheduling result and the pending commands, the DDR2 memory controller can:

∙Mask out the additional data using DDR_DQM outputs

∙Terminate the write burst and start a new write burst

The DDR2 memory controller does not perform the DEAC command until page information becomes invalid.

Figure 9. DDR2 WRT Command

DDR_CLK

DDR_CLK

Sample

Write Latency

DDR_CKE

DDR_CS

DDR_RAS

DDR_CAS

DDR_WE

DDR_A[13:0] COL

DDR_BA[2:0]

BANK

 

 

 

 

 

 

 

DDR_A[10]

 

 

 

 

 

 

 

 

DDR_DQM[3:0]

DQM1 DQM2 DQM3 DQM4 DQM5 DQM6 DQM7 DQM8

 

DDR_D[31:0]

D0

D1

D2

D3

D4

D5

D6

D7

DDR_DQS[3:0]

 

 

 

 

 

 

 

 

2.5Memory Width and Byte Alignment

The DDR2 memory controller supports memory widths of 16 bits and 32 bits. Table 4 summarizes the addressable memory ranges on the DDR2 memory controller.

Table 4. Addressable Memory Ranges

Memory Width

Maximum Addressable Bytes

Address Type Generated by DDR2

 

 

Memory Controller

×16

128 Mbytes

Halfword address

×32

256 Mbytes

Word address

18

DSP DDR2 Memory Controller

SPRUF85 –October 2007

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Contents Users Guide Submit Documentation Feedback Contents List of Figures List of Tables Data Manual Reference GuidesRelated Documents From Texas Instruments Related Documents From Texas Instruments Features Functional Block DiagramPurpose of the Peripheral Industry Standards Compliance Statement Signal Descriptions Clock ControlMemory Map DDR2 Memory Controller Signal Descriptions Pin DescriptionCommand Function DDR2 Sdram CommandsTruth Table for DDR2 Sdram Commands Protocol DescriptionsDdrclk MRS/EMRS Ddrcke Ddrcs Ddrras Ddrcas Ddrwe Mode Register Set MRS and EmrsRefresh Mode COL Activation Actv Ddrcs Ddrras Ddrcas DdrweDcab Command Deactivation Dcab and DeacRead Command DDR2 Read CommandAddressable Memory Ranges Write WRT CommandMemory Width and Byte Alignment Memory Width Maximum Addressable BytesBit Field Bit Value Bit Description Bank Configuration Register Fields for Address MappingAddress Mapping IbankLogical Address-to-DDR2 Sdram Address Map for 16-bit Sdram Logical Address-to-DDR2 Sdram Address Map DDR2 Memory Controller Interface DDR2 Memory Controller Fifo DescriptionDDR2 Memory Controller Fifo Block Diagram Command Ordering and Scheduling, Advanced ConceptCommand Starvation Refresh Urgency Levels Refresh SchedulingPossible Race Condition Urgency Level DescriptionSelf-Refresh Mode Reset ConsiderationsReset Sources DDR2 Sdram Extended Mode Register 1 Configuration 11.1 DDR2 Sdram Device Mode Register Configuration ValuesDDR2 Sdram Mode Register Configuration 11 DDR2 Sdram Memory InitializationInterrupt Support 11.2 DDR2 Sdram Initialization After Reset11.3 DDR2 Sdram Initialization After Register Configuration Edma Event SupportUsing the DDR2 Memory Controller Connecting the DDR2 Memory Controller to DDR2 SdramConnecting to Two 16-Bit DDR2 Sdram Devices Connecting to a Single 16-Bit DDR2 Sdram Device Connecting to Two 8-Bit DDR2 Sdram Devices Programming the Sdram Refresh Control Register Sdrfc Programming the Sdram Configuration Register SdcfgSdcfg Configuration Function SelectionConfiguring Sdram Timing Registers SDTIM1 and SDTIM2 DDR2 Memory Refresh SpecificationSdrfc Configuration SDTIM1 ConfigurationDDR2 Sdram Data Register Field Sheet Parameter SDTIM2 ConfigurationDmcctl Configuration Name DescriptionDDR2 Memory Controller Registers Offset Acronym Register DescriptionModule ID and Revision Register Midr Field Descriptions Module ID and Revision Register MidrDDR2 Memory Controller Status Register Dmcstat Bit Field Value DescriptionSdram Configuration Register Sdcfg Sdram Configuration Register Sdcfg Field DescriptionsSdram Configuration Register Sdcfg Field Descriptions Sdram Refresh Control Register Sdrfc Sdram Refresh Control Register Sdrfc Field DescriptionsTrfc TRP Trcd TWR Sdram Timing 1 Register SDTIM1Sdram Timing 1 Register SDTIM1 Field Descriptions Tras TRC TrrdDDR2 memory data sheet. Calculate using this formula Todt Tsxnr Sdram Timing 2 Register SDTIM2Sdram Timing 2 Register SDTIM2 Field Descriptions Tsxrd Trtp TckeBurst Priority Register Bprio Burst Priority Register Bprio Field DescriptionsPrioraise DDR2 Memory Controller Control Register Dmcctl ReseProducts Applications DSPRfid
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