1#0/7%24.ETWORKANALYSER5SERMANUAL
English
SERIAL COMMUNICATION
Q
4HEREFERENCEDOCUMENTFORALLTHEASPECTSOFTHE-ODBUSASWELLASTHEONLYOFFICIAL
SPECIFICATIONOFTHEPROTOCOLINQUESTIONISTHATFOUNDINTHEWEBSITEWWWMODBUS
ORG4HEDATACOMMUNICATIONSYSTEMBASEDONTHE-ODBUSPROTOCOLMAKESITPOSSIBLE
TOCONNECTUPTOINSTRUMENTSTOACOMMON23LINE4HECOMMUNICATIONTAKES
PLACEINHALFDUPLEXANDONLYTHEMASTER0#0,# ISABLETOINITIATETHEQUESTIONAND
ANSWERTYPEDIALOGUEWITHTHESLAVESADDRESS WITHOUTOBTAININGANYREPLY
Characteristics of the Modbus protocol
s 4YPEOF-ODBUSCODING2452EMOTE4ERMINAL5NIT
s 4RANSMISSIONSPEED"AUDRATE BPSSELECTABLEBYTHEUSER
s "YTEFORMATTRANSMITTEDSTARTBITDATABITSPARITYBITNONEODDEVENASSELECTED
STOPBIT
Message structure
4HEMESSAGEISSTRUCTUREDINVARIOUSFIELDSSTARTADDRESSFUNCTIONDATA#2#CHECK
END MADEUPOFORMORECHARACTERSEACHTHECHARACTERSPERMITTEDFOREACHFIELDARE
THEHEXADECIMALSx!x&THEENTIREMESSAGEHASTOBESENTWITHNOINTERRUPTIONS
ANDIFTHEREISAPAUSELASTINGMORETHANATRANSMISSIONTIMEOFCHARACTERSTHE
receiver has to recognise the incomplete message condition and assume that the
FOLLOWINGBYTEISTHESTARTOFANEWMESSAGE4HESTARTANDENDOFTHEMESSAGECANBE
RECOGNISEDBYASILENTINTERVALOFATLEASTCHARACTERS4HEMESSAGECANBESUMMED
UPASFOLLOWS
START
ADDRESS
FUNCTION
DATA
CRC CHECK
END
T1-T2-T3-T4
8 BITS
8 BITS
#X 8 BITS
16 BITS
T1-T2-T3-T4
Error check calculation procedure
4HE#YCLICAL2EDUNDANCY#HECK#2# FIELDISMADEUPOFTWOBYTESANDCONTAINSA
BITBINARYVALUE4HISVALUEISCALCULATEDBYTHETRANSMITTERDEVICEWHICHINSERTSTHE
#2#INTHEMESSAGE4HERECEIVERDEVICERECALCULATESTHE#2#DURINGTHERECEPTIONOF
THEMESSAGEANDCOMPARESTHEVALUECALCULATEDWITHTHATRECEIVEDINTHEMESSAGE)F
THETWOVALUESDONOTCOINCIDEANERRORCONDITIONISGENERATED
Funzioni Modbus implementate
Read holding register
(03)
Read input register
(04)
&ORCEMULTIPLECOIL
0RESETMULTIPLEREGISTER
MESSAGGIINDIRIZZABILIATUTTIGLISLAVESLAVEADDRESS
Summary of Contents for QC-POWER-T-485
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