Universal Wall-Mount Controller
Modbus Communication Module User Guide
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Introduction
The TUCB & TUHB Series Modbus Communication Module User Guide provides information for using the Neptronic
®
controller communication feature. The uses Modbus communication protocol over serial line in the RTU mode and
provides a Modbus network interface between client devices and Neptronic TUCB & TUHB Series devices.
The TUCB & TUHB Series Modbus Guide assumes that you are familiar with Modbus terminology.
The following are the requirements for Modbus:
•
Data Model
. The controller Modbus server data model uses only the Holding Registers table.
•
Function Codes
. The controller Modbus server supports a limited function codes subset comprising:
o
Read Holding Registers (0x03)
o
Write Single Register (0x06)
o
Write Multiple Registers (0x10)
•
Exception Responses
. The controller Modbus server supports the following exception codes:
o
Illegal data address
o
Illegal data value
o
Slave device busy
•
Serial Line
. The controller Modbus over serial line uses RTU transmission mode over a two-wire configuration
RS485 (EIA/TIA-485 standard) physical layer.
o
The physical layer can use fixed baud rate selection or automatic baud rate detection (default) as per the
Modbus
Auto Baud Rate
device menu item or holding register index 1.
o
The supported baud rates are 9600, 19200, 38400, and 57600.
o
The physical layer also supports variable parity control and stop bit configuration as per the
Modbus Comport
Config
device menu item or holding register index 2.
o
In auto baud rate configuration, if the device detects only consecutive bad frames (2 or more) for one second with
any given baud rate, it will reinitialize itself to the next baud rate.
•
Addressing
. The controller device only answers at the following address:
o
The device's unique address (1 to 246) that can be set through the device menu or through holding register index
0.
