Modbus TCP Server

Introduction

Modbus TCP is not based on a hierarchical structure, but on a client/server model.

Without any configuration, the embedded Ethernet port of the bus coupler supports Modbus server.

Modbus TCP Server

The Modbus server supports the Modbus requests:

Function Code Dec (Hex)	Subfunction Dec (Hex)	Function
3 (3)	–	Read holding register (%MW)
6 (6)	–	Write single register (%MW)
16 (10)	–	Write multiple registers (%MW)
22 (16)	-	Mask write register
23 (17)	–	Read/write multiple registers (%MW)
43 (2B)	14 (E)	Read device identification

Modbus TCP Configuration

To configure your TM3 Ethernet bus coupler as a Modbus TCP slave device, add the bus coupler and select Modbus TCP IO Scanner > TM3BCEIP.

Diagnostic Request

This table contains the data selection code list:

Data Selection Code (hex)	Description
00	Reserved
01	Basic Network Diagnostics
02	Ethernet Port Diagnostic
03	Modbus TCP/Port 502 Diagnostics
04	Modbus TCP/Port 502 Connection Table
05 - 7E	Reserved for other public codes
7F	Data Structure Offsets

TM3 Bus Coupler Modbus TCP Registers

Zone	Access	Registers	Function
Diagnostic Zone	RO	900 - 901	Bus coupler diagnostics
	RO	930 - 931	TM2/TM3 bus status
	RO	932	System state
	RO	991 - 992	Communication diagnostics
	RO	1058...1066	Ethernet communication parameters
	RO	1100...1115	TM3 bus coupler product information
	RO	2512 - 2513	TM3 bus coupler product serial number
IO Scanner Zone	RO	1...99	Subset of bus coupler module input values (first 7 modules)⁽¹⁾
	RW	101...199	Subset of bus coupler module output values (first 7 modules)⁽¹⁾
	RO	3001...3499	Bus coupler module input values (all modules)⁽¹⁾
	RW	3501...3999	Bus coupler module output values (all modules)⁽¹⁾
	RO	13001...13499	Bus coupler module input values (all modules) for use with HMI devices.
	RO	13501...13999	Bus coupler module output values (all modules) for use with HMI devices.
(1) Access to those registers returns an error when System State (register 932) is not 5 (TM3 bus controlled by modbus TCP). The values of registers 3001…3499, 3501…3999, 13001…13999 are valid only when the register 931 is 0 (Bus status OK, All module status OK).

Bus Coupler Diagnostics

Registers	Function	Description
900	Bus coupler diagnostics	Bits (0...8]): Not used
		Bit (9): I/O bus runtime error
		Bits (10-11): Not used
		Bit (13): I/O bus not configured or bus configuration error
		Bits (14-15): Not used
901	I/O modules status	Bit (0...13): Status of first expansion module to status of 14^th expansion module
		Bits (14-15): Not used
		0: No error detected
		1: Error detected

TM3/TM2 Bus Status

Registers	Function	Bits	Description
930	TM3/TM2 bus status	0…1 Module 1	Module status (2 bits per module): o0x0: Module OK o0x1: Module configuration error detected o0x2: Module runtime error detected o0x3: Module not present but it is optional module
		2…3 Module 2
		4…5 Module 3
		6…7 Module 4
		8…9 Module 5
		10…11 Module 6
		12…13 Module 7
		14…15 Module 8
931	TM3/TM2 bus status	0…1 Module 9	Module status (2 bits per module): o0x0: Module OK o0x1: Module configuration error detected o0x2: Module runtime error detected o0x3: Module not present but it is optional module
		2…3 Module 10
		4…5 Module 11
		6…7 Module 12
		8…9 Module 13
		10…11 Module 14
		12…13	Reserved
		14…15	Bus status: o0x0: Bus OK o0x1: Bus configuration error detected o0x2: Bus runtime error detected o0x3: Bus not configured

System State

Registers	Function	Description
932	State of the system	o0x0: System is booting. o0x1: TM3 bus is not configured. o0x2: A TM3 configuration is being transferred. o0x3: A valid TM3 configuration has been applied successfully. The outputs are set to 0. o0x4: TM3 bus is controlled by EIP. o0x5: TM3 bus is controlled by ModbusTCP IO scanner. o0x6: TM3 bus is controlled by Web server. o0x7: Timeout on fieldbus refresh o0x8: Firmware update in progress o0xA: System state transition in progress.
933	TM3/TM2 bus configuration	Bus status: oBits [0]: (Modbus TCP Data consistency o0x0: Disable o0x1: Enable

Registers

Function

Description

932

State of the system

o0x0: System is booting.

o0x1: TM3 bus is not configured.

o0x2: A TM3 configuration is being transferred.

o0x3: A valid TM3 configuration has been applied successfully. The outputs are set to 0.

o0x4: TM3 bus is controlled by EIP.

o0x5: TM3 bus is controlled by ModbusTCP IO scanner.

o0x6: TM3 bus is controlled by Web server.

o0x7: Timeout on fieldbus refresh

o0x8: Firmware update in progress

o0xA: System state transition in progress.

933

TM3/TM2 bus configuration

Bus status:

oBits [0]: (Modbus TCP Data consistency

o0x0: Disable

o0x1: Enable

Communication Diagnostic

Registers	Function	Description
991	Number of received messages	Number of messages received.
992	Number of sent messages	Number of messages sent.

Ethernet Communication Parameters

TM3 Bus Coupler Bus Coupler Product Information

Registers	Function
1100	TM3 bus coupler product code
2507-2508	TM3 bus coupler product firmware version
2512-2513	TM3 bus coupler product serial number
2601	Rotary switch ONEs position
2602	Rotary switch TENs position