Modbus driver

Observe these guidelines when working with Modbus controllers.

Protocols

The Modbus communication driver supports these protocols:
  • Modbus TCP
    . TCP Socket access mode.
  • Modbus RTU
    . Serial port access mode.
    IMPORTANT:
    If the target device is an
    Allen-Bradley®
     embedded device, you must:
    • Set the serial port of the target device to RS-485 with SystemManager.
    • Verify that the terminator resistors are wired correctly
    For more information, see the devices documentation.

Data types

The Modbus communication driver supports these data types:
Data type
Length
Bool
1 bit
Byte
1 byte
SByte
1 byte
UInt16
2 bytes
Int16
2 bytes
UIn32
4 bytes
Int32
4 bytes
Uint64
8 bytes
Int64
8 bytes
Float
4 bytes
Double
8 bytes
String
80 characters by default
Array

Data areas

The Modbus communication driver supports these data areas:
Area
Modbus Function Code (Hex)
Addressing
Data Type
Access
Ranges
Single Coils
01 Read
05 Write (Single)
Coil Status
Boolean
Read/Write
0-65535
Coils
01 Read
15 Write (multiple)
Coil Status
Boolean
Read/Write
0-65535
Discrete Inputs
02 Read
Input Status
Boolean
Read Only
0-65535
Single Register
03 Read
06 Write
Holding Register
Word
Read/Write
0-65535
Multiple Register
03 Read
10 Write
Holding Register
Word
Read/Write
0-65535
Input Register
04 Read
Input Register
Word
Read Only
0-65535
TIP: The addressing may differ from device to device. For more information, refer to the device documentation.
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