XITRON XT2640 - Command Syntax; Special Characters

XT2640OperatingManual 13July2016 Page138of187
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24.1.4.3.3 RegisterandCommandDiffer encestoOth erInter faces
SomeregistersandcommandsaredifferentintheGPIBtothosefortheotherinterfaces,andsomeareonlyavailablefromtheGPIB
interface.
TheLOCALandLOCKOUTcommandsaresilentlyignoredifreceivedviatheGPIBinterface.
TheESRregisterhasadifferentformatthanfortheotherinterfaces,fortheGPIBinterfaceitscontentsareasdefinedbyIEEE488.2.
The*ESE,*ESE?,*SRE,*SRE?,*TST?and*WAIcommands(asdefinedbyIEEE488.2)areavailablefromtheGPIBinterfacebutare
unavailablefortheotherinterfaces.
ForallotherinterfacesifaquerycommandissenttotheXT2640,andthenanotherquerycommandissenttotheXT2640ina
differentsetofcommandsbeforetheresponseofthepriorqueryhasbeenfullytransmittedbytheXT2640thenanerrorisraised
andthesecondquerycommandisdiscarded.FortheGPIBinterfaceifthisoccursthenanerrorisraisedandtheresponsetothe
secondquerycommandreplacesthatofthe1
st
querycommand.ThisisasrequiredbyIEEE488.2.
24.1.4.4 IEEE488.2COMPATIBIL ITY
TheXT2640islargelycompatiblewithmandatoryportionsoftheIEEE488.2standard,howevertheresomedeviations.
TheXT2640doesnotlockuptheGPIBwhenrequestedtotalkandthereisnopriorquerycommandresponsetotransmit,
asrequiredbytheIEEE488.2standard;asdescribedabovetheXT2640respondswithablankresponseinthiscase.
TheXT2640doesnotuseawhitespacecharacterasacommandordataseparatorasrequiredbytheIEEE488.2standard;
inmostcaseswhitespacecharactersareignoredbytheXT2640.
The“pon”bitoftheESRregisterhasanextendedmeaningintheXT2640beyondthatrequiredbyIEEE488.2.
24.2 COMMANDSYNTAX
AllcommandstotheXT2640usethestandard7‐bitASCIIcharactersetusing8‐bitencoding(the8
th
bitiszero)independentofthe
actualinterfacebeingused.Acommandisastreamofcharacters,theXT2640storingreceivedcharactersuntilacommand
terminatorcharacterisreceivedandonlythenisactiontakenonthecommands.Furthercharactersmaybereceivedwhilethe
XT2640istakingtheactionsneededforaprecedingcommandbutnoactionwillbetakenonthemuntilallpendingcommand
decodeactivityiscompleted.
EachcommandisaKEYWORDfielddefiningthecommandpossiblyfollowedbyfurtherfieldswhichrefinetheactionofthe
command.Theavailablecommandkeywordsandthefieldsrequiredforeacharedescribedintableslaterinthissection.
Morethanonecommandcanbepresentinasinglecommandset,inwhichcaseeachcommandisseparatedfromthepreviousbya
commandseparatorcharacter.Ifanerrorisfoundinanycommandwithinacommandsetthenthatcommandandanyremaining
commandswhichfollowitinthecommandsetwillnotbeactioned.
SincetheinterfaceisbasedonstreamingASCIIcharacterstheuseofseparatorandterminatorcharactersisrequiredtoensurethat
theextentsofeachfieldcanbeestablished.Toimprovethereadabilityofcommandsyoumayalsowishtoemploywhitespace
characterstospreadapartfields.
24.2.1 SPECIALCHARACTERS
CertainASCIIcharactersserveaspecialpurposeasdescribedbelow.
24.2.1.1 COMMANDTERMIN ATORC HARACTE RS
Theendofacommandsetisdeterminedbythepresenceofacommandterminatorwhichmaybetheline‐feed,carriagereturn,form
feedorNULL(0value)ASCIIcharacters.
Everythingbetweensuccessivecommandterminatorsisacommandset.Acommandsetislimitedtoamaximumof4095characters
intotal.Thereisnoactiontakenorerrorgeneratedifacommandterminatorisimmediatelyfollowedbyanothercommand
terminator.
24.2.1.2 COMMANDSEPARATORCHAR ACTER
Ifmorethanonecommandisinacommandsettheneachsuccessivecommandisseparatedfromthepreviousbyacommand
separatorwhichisthesemi‐colonASCIIcharacter(;).
Everythingbetweensuccessivecommandseparatorsorcommandterminatorsisacommand.Thereisnoactiontakenorerror
generatedifacommandseparatorisimmediatelyfollowedbyanothercommandseparatororacommandterminator.
24.2.1.3 FIELDSEPARATORC HARACTE R
Mostcommandsrequirecommandfieldswhichrefinetheactionofthecommand;eachfieldisseparatedfromthepreviousbyafield
separatorwhichisthecommaASCIIcharacter(,).
Everythingbetweensuccessivefieldseparators,commandseparatorsorcommandterminatorsisafield.
24.2.1.4 SUB‐FIELDSEPARATORCHAR ACTER
Insomecasesasinglecommandfieldismadeupofseveralsub‐fields;eachsub‐fieldisseparatedfromaprevioussub‐fieldbyasub‐
fieldseparatorwhichisthecolonASCIIcharacter(:).
Everythingbetweensuccessivesub‐fieldseparators,fieldseparators,commandseparatorsorcommandterminatorsisasub‐field.
24.2.1.5 WHITESPAC ECHAR ACTER S
Mostfieldsandsub‐fieldscanhaveoneormorewhitespacecharactersatthebeginningand/orend.Thespace,tabandunderscore
ASCIIcharactersareconsideredaswhitespacecharacters.