Texas Instruments TMS320C6455 manual Activation Actv, Actv Command

Page 16

Peripheral Architecture

www.ti.com

2.4.3Activation (ACTV)

The DDR2 memory controller automatically issues the activate (ACTV) command before a read or write to a closed row of memory. The ACTV command opens a row of memory, allowing future accesses (reads or writes) with minimum latency. The value of DBA[2:0] selects the bank and the value of A[12:0] selects the row. When the DDR2 memory controller issues an ACTV command, a delay of tRCD is incurred before a read or write command is issued. Figure 5 shows an example of an ACTV command. Reads or writes to the currently active row and bank of memory can achieve much higher throughput than reads or writes to random areas because every time a new row is accessed, the ACTV command must be issued and a delay of tRCD incurred.

Figure 5. ACTV Command

ACTV

DDR2CLKOUT

DDR2CLKOUT

DSDCKE
DCE0
DSDRAS
DSDCAS
DSDWE
DEA[13:0]	ROW
DBA[2:0]	BANK
DSDDQM[3:0]

16	C6455/C6454 DDR2 Memory Controller	SPRU970G – December 2005 – Revised June 2011
		Submit Documentation Feedback

Copyright © 2005–2011, Texas Instruments Incorporated

Image 16

Contents Users Guide Submit Documentation Feedback Contents List of Figures List of Tables Submit Documentation Feedback Read This First Read This First Functional Block Diagram FeaturesPurpose of the Peripheral Industry Standards Compliance Statement Clock Control Signal DescriptionsMemory Map DDR2 Memory Controller Signal Descriptions Pin Description DDR2 Sdram Commands Truth Table for DDR2 Sdram Commands Command Function Protocol DescriptionsMode Register Set MRS and Emrs DDR2 MRS and Emrs CommandRefresh Mode Refresh CommandActv Command Activation ActvDcab Command Deactivation Dcab and DeacDeac Command Read Command DDR2 Read CommandWrite WRT Command Memory Width, Byte Alignment, and EndiannessAddressable Memory Ranges Address Type Generated by DDR2Bank Configuration Register Fields for Address Mapping Address MappingBit Field Bit Value Bit Description IbankLogical Address-to-DDR2 Sdram Address Map for 32-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 Scheduling Possible Race ConditionRefresh Urgency Levels Urgency Level DescriptionSelf-Refresh Mode Reset ConsiderationsDevice and DDR2 Memory Controller Reset Relationship DDR2 Memory Controller Reset Effect Initiated by11.1 DDR2 Sdram Device Mode Register Configuration Values DDR2 Sdram Mode Register ConfigurationDDR2 Sdram Extended Mode Register 1 Configuration Mode Register Field11.2 DDR2 Sdram Initialization After Reset 11.3 DDR2 Sdram Initialization After Register ConfigurationInterrupt Support 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 Configuration Register Sdcfg Sdcfg ConfigurationProgramming the Sdram Refresh Control Register Sdrfc FieldDDR2 Memory Refresh Specification Sdrfc ConfigurationConfiguring Sdram Timing Registers SDTIM1 and SDTIM2 SDTIM1 ConfigurationSDTIM2 Configuration Dmcctl ConfigurationDDR2 Sdram Data Register Field Sheet Parameter Name DescriptionOffset DDR2 Memory Controller RegistersRegister Description Module ID and Revision Register Midr Field Descriptions Module ID and Revision Register MidrBit Field Value Description DDR2 Memory Controller Status Register Dmcstat IfrdySdram Configuration Register Sdcfg Sdram Configuration Register Sdcfg Field DescriptionsSequence. Values 4-7 are reserved for this field Sdram Refresh Control Register Sdrfc Sdram Refresh Control Register Sdrfc Field DescriptionsSdram Timing 1 Register SDTIM1 Sdram Timing 1 Register SDTIM1 Field DescriptionsTrfc TRP Trcd TWR Tras TRC TrrdUsing this formula Sdram Timing 2 Register SDTIM2 Sdram Timing 2 Register SDTIM2 Field DescriptionsTodt Txsnr Txsrd Trtp TckeBurst Priority Register Bprio Field Descriptions Burst Priority Register BprioPrioraise DDR2 Memory Controller Control Register Dmcctl DDR2 Memory Controller Control Register DmcctlRevision History Products Applications DSPRfid TI E2E Community Home