Modbus RTU - Instance & Item setup

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Instance

The parameters specific to the Instance setup are related to the initial connection with the Modbus RTU server

Parameter	Description
Address	The address of the Modbus RTU device Integer in range 0-240
Timeout	Timeout in milliseconds Default: 5000
Max Read Registers	Maximum amount of registers read in a single message Note: Some servers allow for specific numbers of registers read in a single message. If this is exceeded, the connection could be refused Default: 123
Write Preset	Chooses which function code used for writing Multiple registers: 0x15 / 0x16 Single register: 0x05 / 0x06 Default: Multiple registers
Endianness	Endianness is documented in this article Default: Big endian
Byte Order	Endianness is documented in this article Default: First byte high
Interframe delay	Interframe delay in milliseconds Default: 200
Serial mode	Choose whether you use RS485 or RS232 as a communication method Default: RS485
Device Interface	Choose which port the Modbus Server is connected to Default: RS485
Baudrate	Choose the baudrate used by the Modbus Server Default: 9600
Parity	Choose the parity used by the Modbus Server Default: None
Databits	Choose the databits used by the Modbus Server Default: 8
Stopbits	Choose the stopbits used by the Modbus Server Default: 1

Item

Parameter	Description
Register	Registers are the addressing syntax used by Modbus. Depending on the register type, chosen below, there are two ways of addressing. Both 5-digit and 6-digit registers are supported When Register Type is Auto Here we use the full address of the register. The first Holding Register will be 40001 or 400001 When Register type is Holding Register (or any other type) Here SIA Connect will automatically fill out the full register syntax. The first Holding Register will be 0
Register Type	Register type defines the method of auto-filling the full register syntax Auto Use the full address syntax for the register. 4000X for Holding registers, etc. Holding Register SIA Connect will automatically fill out the full register syntax. Holding Register 0 equals Register 40001 Input Coil SIA Connect will automatically fill out the full register syntax. Input Coil 0 equals Register 10001 Output Register SIA Connect will automatically fill out the full register syntax. Output Coil 0 equals Register 00001 Input Register SIA Connect will automatically fill out the full register syntax. Input Register 0 equals Register 30001
Type	Chooses both the amount of registers being read, and how they are parsed as data. If a tag is over 1 register, this is where it is chosen. Nothing changes on the addressing syntax, as it is automatically handled by SIA Connect
Floating Point Precision	Defines the decimal precision of Floats

rtu protocol modbus communication