Woodward MRM4, Manual

Page: 187 / 460

Communication Protocols
For detailed information on data point lists and error handling, please refer to the Modbus ® documentation.
To allow configuration of the devices for Modbus ® connection, some default values of the control system must be
available.
Modbus RTU
Part 1: Configuration of the Devices
Call up »Device parameter/Modbus« and set the following communication parameters there:
•
Slave-address, to allow clear identification of the device; and
•
Baud-Rate.
Also, select below indicated RS485 interface-related parameters from there, such as:
•
Number of data bits;
•
One of the following supported communication variants: Number of data bits, even, odd, parity or no
parity, number of stop bits;
•
»t-timeout« : communication errors are only identified after expiry of a supervision time »t-timeout«; and
•
Response time (defining the period within which an inquiry from the master has to be answered).
Part 2: Hardware Connection
•
For hardware connection to the control system, there is an RS485 interface at the rear side of the device
(RS485, fiber optic or terminals).
•
Connect bus and device (wiring).
Error Handling - Hardware Errors
Information on physical communication errors, such as:
•
Bau Rrate Error and
•
Parity Error
can be obtained from the event recorder.
Error Handling – Errors on protocol level
If, for example, an invalid memory address is enquired, error codes will be returned by the device that need to be
interpreted.
Modbus TCP
Establishing a connection via TCP/IP to the device is only possible if your
device is equipped with an Ethernet Interface (RJ45).
Contact your IT administrator in order to establish the network connection.
EN MRM4 01/11 Page 187