Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 351)

Section 8. Operation
351
8.6.2.2 Terminology
Table Modbus to Campbell Scientific Equivalents
(p. 351)
lists terminology
equivalents to aid in understanding how CR800s fit into a SCADA system.
Table 84. 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 CR800
Master Usually a computer
Slave Usually a CR800
Field Instrument Sensor
8.6.2.2.1 Glossary of Terms
Coils (00001 to 09999)
Originally, "coils" referred to relay coils. In CR800s, coils are exclusively
ports, flags, or a Boolean‐variable array. Ports are inferred if parameter
5 of the ModbusSlave() instruction is set to 0. Coils are assigned to
Modbus registers 00001 to 09999.
Digital Registers 10001‐19999
Hold values resulting from a digital measurement. Digital registers in the
Modbus domain are read‐only. In the Campbell Scientific domain, the
leading digit in Modbus registers is ignored, and so are assigned
together to a single Dim‐ or Public‐variable array (read / write).
Input Registers 30001 ‐ 39999
Hold values resulting from an analog measurement. Input registers in
the Modbus domain are read‐only. In the Campbell Scientific domain,
the leading digit in Modbus registers is ignored, and so are assigned
together to a single Dim‐ or Public‐ variable array (read / write).
Holding Registers 40001 ‐ 49999
Hold values resulting from a programming action. Holding registers in
the Modbus domain are read / write. In the Campbell Scientific domain,
the leading digit in Modbus registers is ignored, and so are assigned
together to a single Dim‐ or Public‐variable array (read / write).