Woodward 2301D, Инструкция по установке и эксплуатации, Страница: 107 / 130

Manual 26247 2301D/2301D-EC Digital Control
Woodward 99
Chapter 8.
Communications
Modbus Communication
The 2301D control part numbers 8273-138 and 8273-139 can communicate with
plant distributed control systems or CRT-based operator control panels through
one Modbus communication port. The communication port supports RS-232 and
RS-422 communications using RTU Modbus transmission protocols.
To enable Modbus communication one of the discrete inputs B, C or D should be
configured for “Use Modbus” (Configure Menu B**Discrete In Options**). When
this input is activated the communication port is switched to the settings used in
Service Menu Y**COMM Port (Modbus)**.
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 not programmed (factory default) although it
continues to update all information to all registers. This allows the 2301D to be
monitored but not controlled from an external device. By simply connecting a
monitoring device, configured to communicate through Modbus, and to the
2301D’s defaulted protocol settings (parity, stop bits, etc.), this device can be
used to monitor all the 2301D’s controlling parameters, modes, etc., without
affecting control. To use a 2301D port it must be configured properly.
Monitor And Control
To control the discrete inputs by Modbus, parameter 17 in Service Menu
Y**COMM Port (Modbus)** should be set TRUE. To use the analog Modbus
control, parameter 18 should be set TRUE.
Once a Modbus port is activated by the Modbus selector command, the 2301D
will accept an external network master device. This allows a Modbus-compatible
device to monitor and perform all 2301D mode parameters and commands. To
use a 2301D port it must be configured properly.