7.2.1

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240 AppendixBLogicControl—MIDIImplementation
GlobalControlMessages
HostConnectionandInitialization
Received:
<Hdr>00F7
DeviceQuery
<Hdr>02ssssssssssssssrrrrrrrrF7
HostConnectionReply
<Hdr>0F7FF7
GoOffline
Transmitted:
<Hdr>01ssssssssssssssllllllllF7
HostConnectionQuery
<Hdr>03ssssssssssssssF7
HostConnectionConfirmation
<Hdr>04ssssssssssssssF7
HostConnectionError
ss =Serialnumber(7bytesASCIItext,nonnull-terminated)
ll =Challengecode(4bytes)
rr =Responsecode(4bytes)
OfflineMode:
LogicControlemploysaquerysystemtomaintainaconnectiontothehostsoftware.
WhenLogicControlisinitiallypoweredup,itdefaultstoOfflinemode.InOfflinemode,
LogicControl’sfadersmovetotheirlowestsetting,andtheLCDreads“EMAGICLOGIC
CONTROL--byMACKIE.”Afterpower-on,LogicControlalsotransmitsasystem
exclusiveHostConnectionQuerymessagethatisused(bythehost)todetecta
connection,andwhattypeofdeviceisconnected(LogicControl/LogicControlXT).
CommunicationsInitialization:
WhenthehostsoftwarereceivesaHostConnectionQuerymessage(containingaserial
numberandarandomchallengecode),itshouldtransmitaHostConnectionReply
commandwithin300mstoinitializeLogicControl.Thecommandmustcontainthe
sameserialnumberandthecorrec tresponsecodeforthechallengecode.Hereisthe
algorithm(l1tol4=challengecodebytes1to4,r1tor4=responsecodebytes1to4):
r1=0x7F&(l1+(l2^0xa)–l4);
r2=0x7F&((l3>>4)^(l1+l4));
r3=0x7F&(l4-(l3<<2)^(l1|l2));
r4=0x7F&(l2-l3+(0xF0^(l4<<4)));
LogicControlwill,inturn,respondwitheither:
 aHostConnectionConfirmationmessagethatcontainstheserialnumber,andswitch
toOnlinemode—whereitwillawaitfurtherinstructionsfromthehost,or
 replywithaHostConnectionErrormessage,iftheresponsecodewaswrong.