Modbus TCP Integration with Proxus - Proxus Documentation

What is Modbus TCP?

Modbus TCP is an industrial communication protocol that enables data acquisition from industrial devices over TCP/IP networks. It provides a standardized method for reading data from PLCs, sensors, and other industrial equipment using Ethernet infrastructure.

Device Profile Configuration

Connection Parameters

Configure the communication settings for your Modbus TCP device:

Parameter	Description	Default Value	Range/Format	Required
Host	IP address of the Modbus TCP device	-	IPv4 format	Yes
Port	TCP port number for Modbus communication	502	1-65535	No
ReadingFrequency	Interval between reading cycles (ms)	1000	100-60000	No
ConnectTimeOut	Connection timeout duration (ms)	1000	500-30000	No
ReceiveTimeOut	Response timeout duration (ms)	1000	500-30000	No
DataFormat	Byte order for multi-register data	ABCD	ABCD, BADC, CDAB, DCBA	No

Data Format Options

The DataFormat parameter determines how multi-register values are interpreted:

ABCD: Big-endian, high word first (default)
BADC: Big-endian, low word first
CDAB: Little-endian, high word first
DCBA: Little-endian, low word first

Tag Configuration

Basic Tag Settings

Each tag represents a data point from your Modbus device and requires:

Name: Descriptive identifier for the data point
Address: Modbus address specification
Data Type: Type of data to read
Length: Number of registers to read (for String/Bytes only)
Polling Interval: Individual polling frequency (0 = use device default)

Address Format

[s=station];[x=function];address[.bit]

Address Components

Component	Description	Default	Example
s=station	Modbus station/slave ID	1	s=2
x=function	Read function code	3	x=4
address	Register or coil number	-	100
.bit	Specific bit within a register	-	.5

Function Codes

Function Code	Operation	Address Prefix	Description
01	Read Coils	`x=1;`	Read discrete output coil status
02	Read Discrete Inputs	`x=2;`	Read discrete input contact status
03	Read Holding Registers	(default)	Read holding register values
04	Read Input Registers	`x=4;`	Read input register values

Address Examples

Address Format	Description	Function Code
`100`	Holding register 100	03
`s=2;100`	Register 100 on station 2	03
`x=4;100`	Input register 100	04
`s=2;x=4;100`	Input register 100 on station 2	04
`100.0`	Bit 0 of holding register 100	03
`x=2;100`	Discrete input 100	02
`x=1;100`	Coil 100	01

Data Types

Fixed-Size Data Types

Data Type	Size (Registers)	Size (Bytes)	Description	Range
Bool	-	1 bit	Boolean value (coil/discrete)	true/false
Short	1	2 bytes	Signed short integer	-32,768 to 32,767
UShort	1	2 bytes	Unsigned short integer	0 to 65,535
Int	2	4 bytes	Signed integer	-2,147,483,648 to 2,147,483,647
UInt	2	4 bytes	Unsigned integer	0 to 4,294,967,295
Float	2	4 bytes	Single-precision floating point	IEEE 754 single precision
Long	4	8 bytes	Signed long integer	Large signed integer values
ULong	4	8 bytes	Unsigned long integer	Large unsigned integer values
Double	4	8 bytes	Double-precision floating point	IEEE 754 double precision
DateTime	4	8 bytes	Date and time value	Date and time representation

Variable-Length Data Types

Data Type	Description	Length Usage	Calculation
String	Variable-length string for text data	Required	Characters = Length × 2
Bytes	Variable-length byte data for binary data	Required	Bytes = Length × 2

Configuration Examples

Temperature Sensor

{
  "Name": "Temperature",
  "Address": "s=1;x=4;100",
  "DataType": "Float",
  "Length": 0,
  "PollingInterval": 1000
}

Pump Status

{
  "Name": "Pump Status",
  "Address": "s=2;x=1;50",
  "DataType": "Bool",
  "Length": 0,
  "PollingInterval": 500
}

Device Name String

{
  "Name": "Device Name",
  "Address": "s=2;x=4;400",
  "DataType": "String",
  "Length": 10,
  "PollingInterval": 5000
}

Energy Counter

{
  "Name": "Energy Counter",
  "Address": "s=1;x=4;500",
  "DataType": "UInt",
  "Length": 0,
  "PollingInterval": 2000
}

Variable-Length Data Configuration

String Data Type

Length: Number of registers to read for string data
Character Count: Each register contains 2 ASCII characters
Total Characters: Length × 2

Example: Length = 5 reads 5 registers containing 10 characters

Bytes Data Type

Length: Number of registers to read for binary data
Byte Count: Each register contains 2 bytes
Total Bytes: Length × 2

Example: Length = 4 reads 4 registers containing 8 bytes

Advanced Features

Bit-Level Reading

Read specific bits from registers by adding .bit to the address:

Address: 100.5
Data Type: Bool

This reads bit 5 (0-indexed) from holding register 100.

Dynamic Data Format

Override the default data format for specific tags:

Address: format=BADC;s=2;100
Data Type: Float

This reads a float value using BADC byte order instead of the default ABCD.

Best Practices

Performance Optimization

Group Sequential Addresses: Place related tags in consecutive registers
Optimize Polling Intervals: Use appropriate frequencies based on data change rates
Minimize Station Queries: Group tags by station number
Use Appropriate Data Types: Choose the most efficient data type
Exact Length Sizing: Set Length to match exact data size for String/Bytes

Polling Interval Guidelines

Critical Data: 100-500ms for critical process data
Status Information: 1-5 seconds for status monitoring
Configuration Data: 10+ seconds for slowly changing data

Length Parameter Guidelines

String: Set Length based on expected text length
Bytes: Set Length based on binary data size
Performance: Avoid unnecessarily large Length values
Device Limits: Check device documentation for maximum register ranges

Troubleshooting

Connection Issues

Issue	Possible Cause	Solution
Connection Timeout	Network connectivity, wrong IP/port	Verify network settings and device availability
Connection Refused	Device not responding, firewall blocking	Check device status and network configuration
Intermittent Disconnections	Network instability, timeout settings	Adjust timeout values and check network stability

Data Reading Errors

Issue	Possible Cause	Solution
Invalid Address	Address doesn’t exist on device	Check device documentation for valid address ranges
Data Format Error	Wrong byte order for multi-register values	Adjust DataFormat parameter (ABCD, BADC, etc.)
Function Code Error	Device doesn’t support function code	Try different function codes (03, 04, 01, 02)
Length Parameter Error	Wrong Length for String/Bytes	Set correct Length value for variable data types
Address Range Error	Length exceeds available registers	Reduce Length or check device memory map

Diagnostic Steps

Network Connectivity: Ping the device IP address
Port Accessibility: Verify port 502 is accessible
Address Validation: Check device memory map documentation
Function Code Testing: Try reading with different function codes
Data Format Testing: Test different byte order options
Length Validation: Ensure Length parameter is correct for variable data types

Technical Specifications

Protocol Compliance

Modbus TCP: Full compliance with Modbus Application Protocol v1.1b3
Message ID Management: Automatic increment for request tracking
Error Detection: TCP-based error handling and timeout management
Data Integrity: Built-in validation and retry mechanisms

Performance Characteristics

Maximum Tags: Limited by device capacity and network bandwidth
Update Rate: Configurable from 100ms to 60 seconds per tag
Concurrent Devices: Multiple device connections supported
Data Throughput: Optimized for industrial monitoring applications

Memory Areas

Memory Area	Function Code	Address Prefix	Data Types	Typical Use
Coils	01	`x=1;`	Bool	Digital outputs status
Discrete Inputs	02	`x=2;`	Bool	Digital inputs status
Holding Registers	03	(default)	All types	Process variables, setpoints
Input Registers	04	`x=4;`	All types	Sensor readings, measurements

Overview

Deployment

Data Management

Rules Engine

Functions

Visualization

Integration

Edge Computing

API

​What is Modbus TCP?

​Device Profile Configuration

​Connection Parameters

​Data Format Options

​Tag Configuration

​Basic Tag Settings

​Address Format

​Address Components

​Function Codes

​Address Examples

​Data Types

​Fixed-Size Data Types

​Variable-Length Data Types

​Configuration Examples

​Temperature Sensor

​Pump Status

​Device Name String

​Energy Counter

​Variable-Length Data Configuration

​String Data Type

​Bytes Data Type

​Advanced Features

​Bit-Level Reading

​Dynamic Data Format

​Best Practices

​Performance Optimization

​Polling Interval Guidelines

​Length Parameter Guidelines

​Troubleshooting

​Connection Issues

​Data Reading Errors

​Diagnostic Steps

​Technical Specifications

​Protocol Compliance

​Performance Characteristics

​Memory Areas