Woodward 2301E-ST, Инструкция по установке и эксплуатации

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Manual 26694 2301E-ST
Woodward 100
Chapter 7.
Communications
Modbus Communication
The 2301E-ST control can communicate with plant distributed control systems or CRT based operator
control panels through one Modbus communication port. The communication port supports RS-422
communications using RTU MODBUS transmission protocols. Modbus utilizes a master/slave protocol.
This protocol 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, as defaulted from the factory, is not programmed. Although this port is
not programmed it continue to update all information to all registers. This allows the 2301E-ST 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-ST’s defaulted protocol settings (parity,
stop bits, etc.), this device can be used to monitor all the 2301E-ST’s controlling parameters, modes, etc.
without effecting control. To use a 2301E-ST port it must be configured properly.
Monitor And Control
Once a Modbus port is activated by the Modbus selector command, the
2301E-ST will accept an external network master device. This allows a Modbus compatible device to
monitor and perform all 2301E-ST mode parameters and commands to use a 2301E-ST port it must be
configured properly.
Modbus Communication Mode
The 2301E-ST control supports two Modbus transmission modes. A mode defines the individual units of
information within a message and the numbering system used to transmit the data. Only one mode per
Modbus network is allowed. The supported RTU (Remote Terminal Unit). These modes are defined in the
following table.
Table 7-1. RTU Modbus
Characteristic RTU
Coding System: 8-bit Binary
Start Bit: 1
Data Bits per Character: 8
Parity: None
Stop Bits: 1
Baud Rate: 9600, 19200, 38400, 57600 or 115200
Error Checking: CRC (Cyclical Redundancy Check)
In the RTU mode, data is sent in 8-bit binary characters and transmitted in a continuous stream.
Released