适用于plc的工程应用人员
2)BFM#3,#2Ringlength
Storesthedatathatspecifiesthelengthofthe16-bitcounter(default:K65,536).
UPIntheaboveexample,K100iswrittenintoBFMs#3and#2ofspecialblockNo.2asa32-bitbinaryvalue(BFM#3=0,BFM#2=100).Permittedvalues:K2toK65,536.WhenringlengthK100isspecified,thevalueofthecounterchangesasshownabove.
Note:Writecounterdatawith(D)TO!Countdataisalwayshandledasapairfromtwo16-bitvaluesinthisspecialfunctionblock.16-bit2's
complementvaluestoredintheregistersofthePLCcannotbeused.!WhenyouarewritingapositivevaluebetweenK32,768andK65,535,thedatashouldbetreatedasa32-bit
valueevenwhena16-bitringcounterisused.!Whentransferringcounterdatato/fromthisspecialfunctionblock,alwaysusethe32-bitformsofthe
FROM/TOinstructions((D)FROM,(D)TO).
1.Whenb0issettoONandtheDISABLEinput
terminaltoOFF,thecounterispermittedtostartcountinginputpulses.
2.YH1canturntoON,onlyifb1issettoON.3.YH2canturntoON,onlyifb2issettoON.
4.B3=ON,YH2outputisresetifYH1outputisset,and
YH1outputisresetifYH2outputisset.
B3=OFF,YH1andYH2outputactindependently,
anddonotreseteachother.
5.Whenb4=OFF,presetfunctionbythePRESETinputterminalisdisabled.
6.Whenb8issettoON,allerrorflagsarereset.7.Whenb9issettoON,YH1outputisreset.8.Whenb10issettoON,YH2outputisreset.9.Whenb11issettoON,YH1outputissetON.10.Whenb12issettoON,YH2outputissetON.
4)BFM#11,#10Presetdata
Presetdataisusedtopresetthecurrentvalueofthecounterandwillbecomevalidwhenb4ofBFM#4issettoONandPRESETinputterminalchangesfromOFFtoON.(risingedge)5)BFM#13,#12ComparisonvalueforYH1output,BFM#15,#14ComparisonvalueforYH2output
AftercomparingthecurrentvalueofthecounterwiththevaluewritteninBFM#13and#12,BFM#15and#14,thecomparatorintheVB-1HCoutputsthecomparisonresult.YH1,YH2outputwillnotturnONifyouusePRESETortheTOinstructiontosetthecountervalueequaltothecomparison
value.ItwillturnONonlywhenamatchoccursbythecountingofinputpulses.
Outputoccurswhenthecurrentvaluebecomesequaltothecomparevaluebutonlyifb1andb2ofBFM#4areON.Onceanoutputisset,it
remainsONuntilitisresetbyb9orb10ofBFM#4.Ifb3ofBFM#4isON,however,oneoftheoutputsisresetwhentheotherisset.C
lue
ur6)Countercurrentvalue(BFM#21,20)
Thedefaultvalueofthecounteriszero.
Theinitialcountervaluecanbesetbywritinga32bitvaluedirectlyintoBFM#21and#20(currentvalueofthecounter).
ThecurrentvalueofthecountercanbereadbythePLC.Itwillnotbethecorrectvalueduringhigh-speedoperationsbecauseofthecommunicationdelay.
7)Maximumcountvalue(BFM#23,22),Minimumcountvalue(BFM#25,24)
TheseBFMsstorethemaximumandminimumvalueEVERreachedbythecounter.Ifthepoweristurnedoff,thestoreddataiscleared.BFM#26isforreadingonly.Writecommandsfromtheprogrammablecontrollerareignored,doingsowillcauseM9067ToON.