Schneider Modicon M258 Selection and Upgrade

Schneider Modicon M258 Logic Controller Selection and Upgrade Practical Guide

In the field of industrial automation, the replacement of control systems at the end of the equipment lifecycle is a common but highly challenging task. The Modicon M258 series logic controller launched by Schneider Electric, with its dual core processor, high-density I/O, embedded CANopen master station, and flexible network communication capabilities, is an ideal choice to replace old PLCs such as Modicon TSX Micro or third-party controllers. Whether it is packaging, lifting, conveying, textile or woodworking machinery, M258 can provide a complete solution from simple logic control to multi axis motion control.

This article starts from the perspective of engineer on-site selection and upgrade, systematically reviews the hardware architecture, embedded functions, communication options, expansion modules, and software configuration of Modicon M258, and provides selection suggestions and precautions based on typical application scenarios to help readers quickly complete the modernization transformation of the control system.

Product positioning and core advantages of Modicon M258

1.1 Product positioning

Modicon M258 belongs to Schneider Electric Machine Struxure ™ The core component of "flexible machine control" under the platform is designed specifically for original equipment manufacturers (OEMs). Its target applications include:

Packaging machinery (filling, labeling, sealing)

Lifting and hoisting equipment

Transportation and Storage System

Textile and woodworking machinery

Material handling and assembly line

Compared to early Modicon M238 or third-party small PLCs, M258 has significantly improved in computing speed, I/O expansion capability, and motion control.

1.2 Dual core processor architecture

M258 adopts a dual core processor:

Core 1: Dedicated to real-time execution of application code (logic, motion control, PID, etc.) without interference from communication tasks.

Core 2: Dedicated to handling communication tasks (Ethernet, CANopen, Modbus, Web servers, etc.) to ensure that communication loads do not affect control cycles.

This architecture enables M258 to maintain high response communication with HMI, drivers, and remote I/O while running complex programs.

1.3 Embedded I/O and Storage

M258 offers two basic model sizes, each integrated with:

42 or 66 point digital I/O (including 8 100kHz high-speed counter inputs and 4 reflection outputs)

4-channel analog input (12 bit resolution, voltage or current, limited to TM258xxxx4L model only)

64 MB RAM (Program and Data Storage)

128 MB Flash (Application and Data Backup)

This means that many small and medium-sized applications can be used directly without the need for additional I/O modules, significantly reducing system costs and cabinet space.

Comparison of Replacement and Selection of Old PLCs

2.1 Key points of replacement evaluation

When replacing discontinued controllers (such as Modicon TSX Micro, Siemens S7-200, Mitsubishi FX series) with Modicon M258, it is important to pay attention to the following matching items:

Assessment Item M258 Capability Precautions

The number of digital I/O points in the main body is 42 or 66 points, which can be expanded to 2400 points. To confirm whether the original system exceeds the main body I/O, an additional TM5 module is required

If the original system uses a higher frequency (above 200kHz) for the 8-channel 100kHz (single-phase or two-phase) high-speed counter, the TM5 high-speed counting module needs to be evaluated

Analog input body 4-channel 12 bit (optional) or extended 16 bit module. If the original system analog resolution is 14 bits or more, it is recommended to choose TM5 analog module

The maximum number of motion control axes is 16 (via CANopen). When the original system uses pulse output, Lexium 32 servo+Sercos or pulse control can be selected

Communication interfaces include Ethernet, Modbus serial port, CANopen, and Profibus DP (extension). Check the original fieldbus type and select TM5PCRS2/4 or TM5PCDPS module if necessary

2.2 Typical Replacement Cases

Case: A packaging line originally used Modicon TSX 37-10 PLC to control 5 Altivar frequency converters through CANopen, equipped with 20 point digital I/O and 2 analog inputs.

Upgrade plan:

Select TM258LF42DT4L (with CANopen master station, 42 digital I/O points, 4 analog inputs).

Retain the original CANopen bus and configure communication parameters with the frequency converter.

If the original digital I/O exceeds 42 points, add a TM5 digital expansion module.

Use SoMachine software to convert the original Ladder program (IL/LD/ST are compatible).

Benefits: Processing speed increased by more than 3 times, built-in web server for remote monitoring, and spare parts supply restored to normal.

Detailed explanation of embedded functions

3.1 High speed Counter (HSC)

M258 body integrates 8 high-speed counters, each with a maximum frequency of 100kHz, supporting:

Single phase counting (add/subtract direction)

Dual phase counting (orthogonal encoder, A/B phase)

Reflection output: When the count value reaches the preset threshold, it can directly trigger 4 high-speed outputs with minimal delay, suitable for scenarios such as fixed length cutting and position capture.

Configuration points:

The input type is sink, please note that the external sensor must be matched with NPN or PNP.

The high-speed counter shares a physical point with the regular digital input, and the HSC function needs to be defined in SoMachine before use. The regular input function will be disabled.

3.2 Analog quantity and temperature control

The M258 body analog input can be configured as 0-10V or 0-20mA, with a 12 bit resolution (0~4095). For applications with higher requirements, the TM5 analog expansion module provides 16 bit resolution and multiple ranges.

The controller has built-in PID regulation function, which can be combined with temperature sensors (PT100/thermocouple) to achieve temperature closed-loop control; Simultaneously supporting process control such as pressure and flow.

Attention: To directly connect PT100, a TM5 dedicated temperature module (such as TM5SDI12T) must be used. The analog input of the body does not support resistance sensors.

3.3 Position Control and Motion

M258 supports two motion control modes:

Control Lexium 32 servo or SD3 stepper through CANopen: use PLCopen standard function blocks (MC_Sower, MC_SoveAbsolute, etc.) with up to 16 independent axes. CANopen has a maximum baud rate of 1Mbps and supports synchronous periodic position mode.

Communicate with Lexium 32 or third-party drivers through digital I/O: use high-speed output to send pulse/direction signals, or control start stop, forward and reverse through traditional digital quantities. This method is limited by the number of high-speed output points, but it is easy to implement.

Selection Tips:

The TM258LF series (with CANopen) only supports multi axis motion control.

If more complex electronic cam, gear synchronization and other functions are needed, it is recommended to consider a higher-order Modicon LMC058 motion controller.

Communication interface and network integration

4.1 Embedded Ethernet

All M258 models are equipped with an RJ45 Ethernet port (10/100Mbps, MDI/MDIX adaptive), supporting the following protocols:

Modbus TCP Server/Client (up to 8 server connections)

EtherNet/IP devices (up to 16 connections)

SoMachine protocol (used for programming and debugging, occupying 1 connection)

Web server (up to 10 concurrent connections)

FTP server (for file transfer)

SNMP (Network Management)

Practical functions:

The built-in web server provides a device status page, allowing users to view variables, I/O status, and diagnostic information through a browser without the need for additional programming.

FTP servers can be used for remote uploading/downloading of program files or data logs.

4.2 Serial Link (Modbus/ASCII)

M258 provides an RJ45 serial port that can be configured as RS232 or RS485, supporting:

Modbus RTU/ASCII master or slave

Free protocol (ASCII string transmission and reception)

This port is suitable for connecting old-fashioned instruments, barcode scanners, third-party inverters, etc.

Attention to wiring: Shielded twisted pair cables should be used for RS485 wiring, and terminal resistors should be added at both ends. RS232 is a 3-wire system (Tx/Rx/GND) with a maximum length of 15 meters.

4.3 CANopen Master Station (LF model only)

The TM258LF series (LF42DT, LF42DT4L, LF42DR, LF66DT4L) is equipped with a 9-pin SUB-D interface CANopen master station, which complies with the CiA DS301 V4.0 standard. Features:

Baud rate 125kbps~1Mbps can be set

Supports up to 63 slave nodes

Support PDO, SDO, NMT, heartbeat, and synchronized objects

Import EDS files through SoMachine's built-in CANopen configurator to easily configure drivers, I/O modules, and more.

Typical application: Connect multiple Altivar frequency converters or Lexium servos through CANopen to achieve speed synchronization, torque control, and status monitoring.

4.4 Profibus DP extension (via TM5PCDPS module)

For systems that require access to the Profibus DP bus (such as communication with Siemens S7-300/400 main station), the M258 can be equipped with a TM5PCDPS communication module (occupying one PCI slot). This module uses M258 as a Profibus DP-V1 slave and supports up to 244 bytes of input/output data.

Configuration steps:

Insert TM5PCDPS into the PCI slot of M258 (limited to TM258LD42DT4L, LF42DT4L, LF42DR, LF66DT4L models only).

Use SoMachine to configure the station address and baud rate (up to 12Mbps) of the module.

Import GSD files on the main station side (such as S7-300) and configure I/O mapping.

Note: A M258 can accommodate up to two communication modules, but only one Profibus DP module can be installed (the other slot can be used for the serial port expansion module TM5PCRS2/4).

Expansion I/O and TM5 module selection

M258 increases I/O points or special functions through TM5 series expansion modules. The expansion module includes:

Digital module: 8/16/32 channels, input/output/hybrid type

Analog module: 2/4/6/8 channels, 12 or 16 bits, voltage/current/thermocouple/RTD

High speed counting module: up to 200kHz, supports more counters

Public distribution module: provides unified power distribution for multiple modules

Transmission/reception module: used for remote I/O expansion (up to 100 meters, up to 25 islands)

Scalability:

The maximum number of total I/O points is 2400

Each M258 can connect up to 63 TM5 expansion modules (subject to current consumption and configuration limitations)

Selection suggestion:

For a large number of digital I/O, 16 or 32 channel modules are preferred to save space and cost.

When analog signals require isolation or high precision, choose a 16 bit module (such as TM5SAI4L).

When high-speed counting exceeds 8 channels, specialized modules such as TM5SSC2 (2-channel, 200kHz) should be selected.

Key points for installation and debugging

6.1 Mechanical Installation

The M258 and TM5 modules are designed for DIN rail installation (35mm symmetrical rail) and secured with a top locking rod.

Automatic electrical connections between modules are achieved through side expansion bus connectors, without the need for additional wiring.

When installed horizontally, the ambient temperature is -10~60 ℃, and when installed vertically, it is -10~50 ℃.

6.2 Electrical Wiring

The power terminal is a pluggable spring type, which can be connected by pressing without the need for a screwdriver, and has test holes.

High speed input/output uses dedicated shielded cables and is wired separately from the power line.

The grounding terminal must be reliably connected to the cabinet grounding strip (resistance<100 Ω).

6.3 Software Configuration

Use SoMachine (V4.1 or higher) for programming and configuration.

Supports all IEC 61131-3 languages (IL, LD, FBD, SFC, ST) and CFC.

Built in CANopen and Ethernet/IP configurator, capable of graphically configuring communication parameters.

First power on process:

Connect the PC to M258 via mini USB or Ethernet.

Create a new project in SoMachine and select the correct M258 model.

Use the 'Scan Network' function to automatically identify controllers, download empty programs, and set IP addresses.

If you need to replace the old PLC, you can use SoMachine's "import" function to convert programs from other brands (manual adjustment of instruction mapping is required).

Common Problems and Solutions

Possible causes and solutions for the problem phenomenon

The controller is not running (RUN light is off), no valid program has been downloaded, or it is in STOP state. Modify the controller status to RUN online through SoMachine; Check the program for no compilation errors

CANopen communication failed due to baud rate mismatch, terminal resistance not added, and duplicate checking of all nodes' baud rates for slave addresses; Add 120 Ω resistors at both ends of the bus; Ensure that the station address is unique

The high-speed counter does not count the input value, and the polarity of the wiring is incorrect or the HSC function is not configured to confirm that the sensor type (leakage/source) matches; Enable HSC and allocate inputs in SoMachine

The analog reading fluctuates greatly, and shielded wires are not used or poorly grounded. Twisted shielded wires are used, and the shielding layer is grounded at one end; Add software filtering

Ethernet cannot connect due to IP address conflict or network cable failure. Use MAC address default IP (169.254. x.x) for temporary access; Check the network port indicator light

The Profibus DP module has no response. The GSD file is not installed correctly, and there is a station address conflict. The GSD of TM5PCDPS is installed on the main station side; Check the LED status on the module (green running)

Spare parts and maintenance recommendations

RTC battery: M258 has a coin shaped lithium battery (CR2032) inside for real-time clock. The lifespan is about 5 years, and it can monitor battery voltage alarms in SoMachine.

Firmware upgrade: M258 firmware can be upgraded through a USB storage stick or SoMachine. Be sure to back up the application before upgrading.

Spare parts reserve: It is recommended to stock at least one M258 controller of the same model and commonly used TM5 modules (such as TM5SDI12D, TM5SDO12T) to cope with sudden failures.

Program backup: Regularly use SoMachine to upload programs and save them to a secure location; Programs and configuration files can also be stored on a USB memory stick and inserted into the USB-A port of the M258 for quick recovery.