Overview

Modbus is a serial communication protocol developed by Modicon originally for communication in their line of Programmable Logic Controllers. The protocol was published and released for royalty free industry use as a standard communication path between instruments and controllers and over the years has become a de facto industry standard. Modbus is now the most commonly used protocol for communications between industrial devices.

Modbus communications over an Ethernet connection is called Modbus TCP and Modbus over other serial communication physical layers is commonly implemented as Modbus RTU (binary format characters in the messages) and Modbus ASCII (ASCII characters in message). With the Modbus option, both Modbus TCP Server over the Ethernet port as well as Modbus RTU Slave over the RS-232 (PC) port are supported.

Modbus in the IntelliLogger

The IntelliLogger can be provided with the Modbus option at time of order. Using the Modbus communication protocol, external Modbus capable equipment can communicate with the IntelliLogger simultaneous to its execution of data logging, alarming and reporting function. Modbus communication with the IntelliLogger allows the external device (a PC, a controller, a display, etc) to interface as follows with the IntelliLogger… providing the communicating device has the necessary permissions:

CURRENT VALUE READING
Current values, whether they be analog values, calculated values, event states or any other I/O parameter can be read from the IntelliLogger. This is implemented by the addition of Probe Point icons into the IntelliLogger Program Net  and the assignment of a Modbus register number to the Probe Point.

REMOTE CONTROL UPDATE
Via Modbus, Remote Control (On/Off) icon states within the Program Net can be updated. This facilitates remote control of actions within the IntelliLogger from a remote instrument over the Modbus link.

PROGRAMMABLE CONSTANT UPDATE
Via Modbus, the Programmable Constant icon with the IntelliLogger Program Net can be updated. This allows a remote device to change setpoints, alarms, constants used in calculations, etc via the Modbus link.