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2.4.5Write(WRT)Command
DDR_CLK
DDR_CKE
DDR_CS
DDR_WE
DDR_CAS
DDR_DQM[3:0]
DDR_D[31:0]
DDR_A[12:0]
DDR_RAS
DDR_DQS[3:0]
COL
BANK
DDR_A[10]
DDR_BA[2:0]
DQM7
Sample
D0 D1 D2 D3 D4 D5 D6 D7
DQM1 DQM2 DQM3 DQM4 DQM5 DQM6 DQM8
Write Latency
DDR_CLK
PeripheralArchitecture
PriortoaWRTcommand,thedesiredbankandrowareactivatedbytheACTVcommand.Followingthe
WRTcommand,awritelatencyisincurred.WritelatencyisequaltoCASlatencyminus1.Allwriteshave
aburstlengthof8.TheuseoftheDDR_DQMoutputsallowsbyteandhalfwordwritestobeexecuted.
Figure9showsthetimingforawriteontheDDR2memorycontroller.
Ifthetransferrequestisforlessthan8words,dependingontheschedulingresultandthepending
commands,theDDR2memorycontrollercan:
•MaskouttheadditionaldatausingDDR_DQMoutputs
•Terminatethewriteburstandstartanewwriteburst
TheDDR2memorycontrollerdoesnotperformtheDEACcommanduntilpageinformationbecomes
invalid.
Figure9.DDR2WRTCommand
DDR2MemoryController 18SPRU986B–November2007
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