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7.8.1PLL2ControllerDevice-SpecificInformation
TMS320C6454
Fixed-PointDigitalSignalProcessor
SPRS311A–APRIL2006–REVISEDDECEMBER2006
7.8.1.1InternalClocksandMaximumOperatingFrequencies
AsshowninFigure7-23,theoutputofPLL2,PLLOUT,isdividedby2anddirectlyfedtotheDDR2
memorycontroller.ThisclockisusedbytheDDR2memorycontrollertogenerateDDR2CLKOUTand
DDR2CLKOUT.Notethat,internally,thedatabusinterfaceoftheDDR2memorycontrollerisclockedby
SYSCLK2ofthePLL1controller.
ThePLLOUT/2clockisalsofedbackintothePLL2controllerwhereitbecomesSYSREFCLK.DividerD1
ofthePLL2controllergeneratesSYSCLK1fortheEthernetmediaaccesscontroller(EMAC).TheEMAC
usesSYSCLK1togeneratethenecessaryclockforeachofitsinterfaces.DividerD1shouldbe
programmedto÷2mode[default]whenusingtheGigabitMediaIndependentInterface(GMII)modeand
to÷5modewhenusingtheReduceGigabitMediaIndependentInterface(RGMII).DividerD1issoftware
programmableand,ifnecessary,mustbeprogrammedafterdeviceresetto÷5whentheRGMIImodeof
theEMACisused.Notethat,internally,thedatabusinterfaceoftheEMACisclockedbySYSCLK3ofthe
PLL2controller.
NotethatthereisaminimumandmaximumoperatingfrequencyforPLLREF,PLLOUT,andSYSCLK1.
Theclockgeneratormustnotbeconfiguredtoexceedanyoftheseconstraints.ForthePLLclocksinput
andoutputfrequencyranges,seeTable7-31.Also,whenEMACisenabledwithRGMIIorGMII,CLKIN2
mustbe25MHz.
Table7-31.PLL2ClockFrequencyRanges
CLOCKSIGNALMINMAXUNIT
PLLREF(PLLEN=1)12.526.7MHz
PLLOUT250533MHz
SYSCLK1
(1)
50125MHz
(1)SYSCLK1restrictionappliesonlywhentheEMACisenabledandtheRGMIIorGMIImodesareused.SYSCLK1mustbeprogrammed
to125MHzwhentheGMIImodeisusedandto50MHzwhentheRGMIImodeisused.
7.8.1.2PLL2ControllerOperatingModes
UnlikethePLL1controllerwhichcanoperateinbypassandaPLLmode,thePLL2controlleronly
operatesinPLLmode.Inthismode,SYSREFCLKisgeneratedoutsidethePLL2controllerbydividingthe
outputofPLL2bytwo.
ThePLL2controllerisaffectedbypower-onresetandwarmreset.DuringtheseresetsthePLL2controller
registersgetresettotheirdefaultvalues.TheinternalclocksofthePLL2controllerarealsoaffectedas
describedinSection7.6,ResetController.
PLL2isonlyunlockedduringthepower-upsequence(seeSection7.6,ResetController)andislockedby
thetimetheRESETSTATpingoeshigh.Itdoesnotloselockduringanyoftheotherresets.
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