Schneider TSX17 serial communication upgrade and replacement

Schneider TSX17 serial communication upgrade and replacement

Introduction: Communication Challenges of the Old TSX 17 Micro PLC

Among numerous industrial systems that have been in service for over 20 years, Schneider Electric's TSX 17 series micro PLCs still undertake important control tasks. These devices have compact structures and high reliability, especially suitable for small automation equipment, packaging machinery, specialized machine tools, and other scenarios. However, over time, users are facing two tricky issues:

Communication module shutdown: Key components such as TSX SCG 1131 (RS232 serial port module), TSX SCG 1161 (UNI-TELWAY bus module), and TSX 17 ACC5 adapter are no longer in production, and original spare parts are almost extinct.

Difficulty in integrating with upper level systems: Old systems only support RS232 or UNI-TELWAY dedicated buses, while modern monitoring systems commonly use open protocols such as Ethernet/IP, Profinet, Modbus TCP, making data acquisition and remote control extremely difficult.

For factories that rely on TSX 17, completely replacing the entire control system is costly and carries significant risks. Therefore, a more realistic strategy is to have a deep understanding of the working principles and configuration methods of existing communication modules, master troubleshooting techniques, and, when necessary, perform "precise replacement" through second-hand markets or protocol conversion technologies.

This article will focus on the two core communication solutions of TSX 17 series - asynchronous serial communication (RS232) and UNI-TELWAY fieldbus, providing a complete set of technical references from hardware functions, software configuration, master-slave communication mechanism, troubleshooting to upgrade and replacement paths.

Asynchronous Serial Communication Module TSX SCG 1131

2.1 Module positioning and basic characteristics

TSX SCG 1131 is a single channel asynchronous serial communication module for TSX 17-20 micro PLC, mainly used for exchanging data with external devices with RS232C interface. Typical applications include:

Connect to the upper monitoring computer (SCADA)

Connect a serial printer or barcode scanner

Connecting a modem for remote maintenance

Communicate with other PLCs or smart meters

Electrical interface: RS232C, full duplex (capable of simultaneous transmission and reception), character transmission. The maximum transmission distance is limited by the RS232 standard (usually within 15 meters), but can be extended through a modem.

Data exchange capability: Each frame can transmit up to 30 bytes, suitable for application scenarios of medium to short data packets (such as recipe download, status reading, alarm reporting).

2.2 Programmable configuration of communication parameters

All communication parameters of TSX SCG 1131 are programmed through PL7-2 software (with specific language card: TSX P17 20 FC2/FD2), rather than through hardware dip switches. This brings flexibility, but also requires engineers to be clear about the meaning of each parameter.

Configuration process: Users need to send an 8-word configuration table through the Text Function Block at the beginning of the program. Each word (Word) in the table defines the following parameters in code form:

Parameter optional range description

Function specifies the channel operation mode or transmission protocol such as character mode, Modbus, etc

Data bit length of 7 or 8 bits defines character format

Parity check: No parity check, odd parity check, even parity check are used for error detection

Stop bit 1 or 2 is used for character spacing

Baud rate 150~19200 bps standard rate, does not support higher rates

Send echo enable/disable, wait for echo after sending, timeout triggers error

Receive echo enable/disable. Immediately send back the received characters as they are online

Engineering Tip: When communicating with a PC serial port, typically 8 data bits, no parity check, 1 stop bit, 9600 or 19200 bps are used. The echo function is generally disabled unless a specific handshake protocol is required.

2.3 Transmission/reception dialogue mechanism

After configuration is complete, users perform data exchange by programming text blocks and assigning request codes. The supported request types include:

Sending with timeout (can be paired with confirmation): suitable for scenarios where it is necessary to ensure that the other party receives it

Sending without timeout/confirmation: broadcast style one-way communication

Receive with timeout: wait for a specified number of characters, abort upon timeout

Unconfirmed reception: continuous reception without returning confirmation

Sending/receiving combination: Half duplex response communication (such as inquiry response)

Each frame of data has a maximum of 30 characters. In practical projects, multiple frames are often concatenated to achieve longer data transmission, but the application needs to manage frame segmentation and reassembly.

2.4 Operation monitoring and command control

The module provides Status Words for the PLC program to read and confirm the communication status. Common status indicators include: