Campbell Scientific CR3000 CR3000 Micrologger - Page 373

Section 8. Operation 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 (00001 to 09999) Originally, "coils" referred to relay coils. In CR3000s, 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). RTU / PLC Remote Telemetry Units (RTUs) and Programmable Logic Controllers (PLCs) were at one time used in exclusive applications. As technology increases, however, the distinction between RTUs and PLCs becomes more blurred. A CR3000 fits both RTU and PLC definitions. 373