Cyrus CD T - MC‐Bus System; MC‐BUS Internal Signal Routing; MC‐BUS System Tests

MC‐BUSSYSTEM
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©CyrusAudioLtdJun2014 12 CDtServiceManualIssue1
TheMC‐BUSsystem
MC‐BUSis asystemwhichprovidescommunicationbetween thecontrolsystemsofa  number of
Cyrus products. The communication takes the form of a serial data stream which is sent from a
'master'productandreceivedandrepeatedby'slave'products.Thedataisthuspassedfromone
product to another around a loop. The master product should then receive the message back
whichconfirmsthatloopconnectionshavebeencorrectlymade.TheCDplayerisa'slave'product
and listens for 'CD' commands from the master product in the loop (usually an amplifier or
surrounddecoder).
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MC‐BUSinternalsignalrouting
MC‐BUScontrolisprovidedbythesystemmicrocontrollerIC701.Thesignalsarebufferedintoand
outofthisICasshowninthediagram,TheresistorbiasattheMC‐BUSinputensuresthattheline
idleshigh(+5V)ifnoMC‐BUSconnectionismadetoanotherproduct.
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MC‐BUSsystemtests
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The MC‐BUS system can be tested by connecting the CD player into a known working Cyrus
system.NotethatMC‐BUSmustbeconnectedasaclosedloopassh owninthediagrambelow.It
isalsoimportanttoconnecttheaudiosignalcablesbetweencomponentstoprovideanadequate
ground return path for the MC‐BUS signals. Switch on the power  to the system and set all
components to Standby . Selecting the CD input on the amplifier or switching on a surround
decoder will now activate the CD player. When the amplifier is set to Standby, all other
components
connectedtotheMC‐BUSloopwillalsosettoStandby.
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CDplayer
Amplifier
MC‐Busoutput
MC‐Busoutput
MC‐Businput
MC‐Businput
IC401F
+5V
IC401E
IC401A
IC401B
IC701
MCBusout
MCBusin
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