Crestron CNX-BF12 Dokumentacja Pobierz pdf (Strona 69)

EssentialsofCrestronProgramming

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69

TheInterlocksymbolwilllatchanoutputhighontherisingedgeofitscorresponding

input.Inaddition,anyotheroutputsignalthatwaspreviouslyhighwillbelatchedoff.

Thusthissymbolwillhaveatmostoneoutputhighatanygiventime.Thispropertyis

calledbreakbeforemake.Inesse

nce,thissymbolwillrememberwhichinputwaslast

drivenhigh,makingitveryhandywhentheuserhastoselectfromanumberofchoices.

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IntheVirtualPresentationRoomprogramthissignifiesthatwhentheuserpressesthe

ScreenUpbutton,thiswilltriggertheScreenUpinputoftheinterlocksymbol,latching

theScreen_Up_FBoutputhigh.Sincethisoutputisthedrivingsourceofthe<fb21>

inputofthetouchpanel,thebuttonwillshowactivefeedbackforaslongastheScreen

Upinterlockislatchedhi

gh.

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Similarly,whentheuserpressestheScreenDownbutton,thi

swilltriggertheScreen

DowninputoftheInterlocksymbol,latchingthecorrespondingoutputhigh,and

activatingthecorrespondingbuttonfeedback.

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NotethatinthisexampletheoutputsignalsoftheInterlocksymbolarebeingusedfor

feedbackonly,andarenotbeingroutedtotheC2Icardtoopenandclosetherelays.

ThisisbecausetheoutputsoftheInterlockarelatched,anditisgenerallyconsidered

poorprogrammingtodrivemomentaryfunctions(suchasarelaycommand)witha

latchingsignal,eventhoughinsomecasesitmaywork corr

ectly.Sincewehave

momentarysignalsalreadyontheinputsideofthesymbol,itis“cleaner”tousetheseto

drivetherelays.

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WehaveseenhowtheIn

terlockandTogglesymbolsareevent‐driven; thatis,whenan

event(arising‐edgetransition,forexample)occursthesymboldrivesitsoutputsignals

totheappropriatelevels.Sometimesthisisnotsufficient,however,andyouneedto

controlwhenthingswillhappen.Inthecaseofrelaycontrols,thecontrolledscreenne

eds

tobeassertedforaperiodoftime,asspecifiedbythemanufacturer.TheOneShot

symbolallowsthistypeoftime‐basedcontrol.

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Crestron CNX-BF12 Dokumentacja Strona 69