Woodward 2301E, Инструкция по установке и эксплуатации, Страница: 147 / 182

Manual 26641 2301E Digital Control
Woodward 137
Chapter 8.
Communications
Modbus Communication
The 2301E control can communicate with plant distributed control systems or
CRT-based operator control panels through the RS-422 communication port. The
communication port supports RS-422 communications using RTU Modbus
transmission protocols.
Modbus communications is set for default on the RS-422 serial port and the
settings used in Service Menu Z**COMM PORTS**.
Modbus utilizes a master/slave protocol which determines how a communication
network’s master and slave devices establish and break contact, how a sender is
identified, how messages are exchanged, and how errors are detected.
Monitor Only
The Modbus communication port is programmed to update all information to all
registers. This allows the 2301E to be monitored, but not controlled from an
external device. By simply connecting a monitoring device, configured to
communicate through Modbus, and to the 2301E
’s defaulted protocol settings
(parity, stop bits, etc.), this device can be used to monitor all the 2301E
’s
controlling parameters, modes, etc., without affecting control. To use the 2301E
port, it must be configured properly.
Monitor and Control
To control the inputs by Modbus, parameter
“01 ENABLE MODBUS CONTROL
in Service Menu Z**COMM Port** should be set TRUE.
Once a Modbus port is activated by the Modbus selector command, the 2301E
will accept an external network master device. This allows a Modbus-compatible
device to monitor and perform all 2301E mode parameters and commands. To
use a 2301E port it must be configured properly.
Modbus Control, when activated, is in parallel with the Discrete Inputs through an
“OR” input. This means that the Discrete Inputs
or the Modbus inputs have
control over each the functions.