Modbus RTU Master(Client)

Supported Devices and Requirements

	Description	Notes
Distributor	MODICON
Device	Any device that supports MODBUS RTU
Comm. Module
Comm. Method	Serial (RS232c , RS422, RS485)
Protocol	MODBUS RTU
Driver Description	MODICON Modbus RTU Mode

Communication Settings

Station

Swap Word In Case Of Float Data (32 Bits): MODBUS protocol does not define how the 32-bit data is transferred. Because of this, the way bytes are transferred may differ depending on the devices. This option lets the user adjust byte orders so that upper 16-bit data and lower 16-bit data get swapped when the data is transferred to the target device.

Swap Word In Case Of 32 Bits Integer Data: This swap option is for the 32-bit integer data (INT32, UINT32, BCD32, UBCD32).

COM BLOCK

Kind of Data : Sets one of the following data types: Coil Status (Digital) / Input Status (Digital) / Holding Register (Analog) / Input Register (Analog)

Data Type	Type	R/W	Identifier	No. of data	Function code
Coil Status	Digital	Read/Write	0	2000	1(5)
Input Status	Digital	Read Only	1	2000	2
Input Register	Analog	Read Only	3	125	4
Holding Register	Analog	Read/Write	4	125	3(6)

Identifier means that the tag’s address in UltimateAccess Web must start with it. For example, using Coil Status and its address 102 means that the address is 00102.

Function code means the MODBUS protocol’s command code used to read the corresponding data type in this I/O driver. The code in the brackets are used to write the corresponding data type.

Address : After deciding the identifier, designate the starting address of the block. It must be within the range of 1 to 65536.
No. of data : Sets the number of data to read, starting from the address assigned to Address. For digital types, the number of data is always in bits. For analog types, the number of data is always in words.

Address Format

Address format (Analog, Digital)

Identifier

Address

Address format (Bit data from Analog)

Identifier

Address

.

Bit number

Identifier : All the MODBUS addresses should start with the identifier. If the user tries to read bit data from an analog address, the identifier must be either 3 or 4, and it’s read-only.
Address : Enter the starting address of the data to read from. It can range from 1 to 65536. In case of using hexadecimal number to indicate the address, add 'h' at the end of the address. (Example : 100FFh = 255th Input Status)
Bit number : Enter a value that ranges from ‘0’ to ‘F’. Only hexadecimal value is allowed.
Example 1 : “10009” = 9th address of Coil Status
Example 2 : “41001.F” = 16th bit in 1001st address of Holding Register