
Section 8. Operation
373
Table 91. Modbus to Campbell Scientific Equivalents
Modbus Domain Data Form Campbell Scientific Domain
Coils Single Bit Ports, Flags, Boolean Variables
Digital Registers 16-bit Word Floating Point Variables
Input Registers 16-bit Word Floating Point Variables
Holding Registers 16-bit Word Floating Point Variables
RTU / PLC CR3000
Master Usually a computer
Slave Usually a CR3000
Field Instrument Sensor
8.6.2.2.1 Glossary of Terms
Coils(00001to09999)
Originally,"coils"referredtorelaycoils.InCR3000s,coilsareexclusively
ports,flags,oraBoolean‐variablearray.Portsareinferredifparameter
5oftheModbusSlave()instructionissetto0.Coilsareassignedto
Modbusregisters00001to09999.
DigitalRegisters10001‐19999
Holdvaluesresultingfromadigitalmeasurement.Digitalregistersinthe
Modbusdomainareread‐only.IntheCampbellScientificdomain,the
leadingdigitinModbusregistersisignored,andsoareassigned
togethertoasingleDim‐orPublic‐variablearray(read/write).
InputRegisters30001‐39999
Holdvaluesresultingfromananalogmeasurement.Inputregistersin
theModbusdomainareread‐only.IntheCampbellScientificdomain,
theleadingdigitinModbusregistersisignored,andsoareassigned
togethertoasingleDim‐orPublic‐variablearray(read/write).
HoldingRegisters40001‐49999
Holdvaluesresultingfromaprogrammingaction.Holdingregistersin
theModbusdomainareread/write.IntheCampbellScientificdomain,
theleadingdigitinModbusregistersisignored,andsoareassigned
togethertoasingleDim‐orPublic‐variablearray(read/write).
RTU/PLC
RemoteTelemetryUnits(RTUs)andProgrammableLogicControllers
(PLCs)wereatonetimeusedinexclusiveapplications.Astechnology
increases,however,thedistinctionbetweenRTUsandPLCsbecomes
moreblurred.ACR3000fitsbothRTUandPLCdefinitions.
Komentáře k této Příručce