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ICC
11.12.2
Modbus RTU
11.12.2.1
Modbus RTU Master
11.12.2.1.1 Overview
The gateway supports the Modbus RTU master protocol on its RS-485 port.
Some notes of interest are:
•
Supported Modbus master functions are indicated in Table 11.
Table 11: Supported Modbus RTU Master Functions
Function
Code
Function
01
Read Coil Status
02
Read Input Status
03
Read Holding Registers
04
Read Input Registers
05
Force Single Coil
06
Preset Single Register
15
Force Multiple Coils
16
Force Multiple Registers
•
Requests are fully configurable through service objects.
•
32-bit register accesses are supported in a variety of options and formats.
•
The following point types are supported in Modbus Service Objects:
o
Holding Register
o
Input Register
o
Coil Status
o
Input Status
11.12.2.1.2 Modbus Service Objects
The Modbus RTU master driver uses service objects to describe what services
the gateway should perform. For each service object, the gateway will continually
read the registers or discretes defined within the service object from the
designated slave, storing the value(s) in the database (if the read function is
enabled). When data in the database changes where the registers or discretes
are mapped, a write request is generated to the designated slave notifying it of
the changed register or discrete value(s) (if the write function is enabled). For
more information on configuring Modbus service objects, refer to section
8.8.11.2.
