Modicon SA85 Linux Driver Development Guide: PCI-85 Industrial Communication Card Driver Porting

Introduction to Modicon SA85/PCI-85

Supported Hardware

The open-source Linux driver projects recommended by modbus.org are hosted on SourceForge:sourceforge. net/projects/modp-driver. The license is BSD license, which includes complete driver source code and usage examples.

Supported Hardware and Kernel Versions by Driver

• Support hardware: Modicon ISA SA85 and PCI-85 Interface Cards
• Linux Kernel Versions: 2.2.19 and above, 2.4.7 and above
• License: BSD License
• Content: Driver source code+sample client program

Compilation and installation of drivers

Driver source code needs to be compiled on the target Linux system. The following steps use commands from the old version kernel (2.4. x), while modern kernels (5. x/6. x) need to be adapted:

# 下载源码
git clone https://git.code.sf.net/p/modp-driver/code modp-driver
cd modp-driver

# 编译（需要内核头文件）
make

# 加载驱动模块
insmod sa85.o

# 或对于 PCI 版本
insmod pci85.o

# 检查驱动是否加载成功
dmesg | tail -20
lsmod | grep -E 'sa85|pci85'

# 查看设备节点
ls -la /dev/sa85* /dev/pci85*

Regarding Modbus Plus protocol

Modbus Plus (MB+) is a proprietary token passing network developed by Schneider Electric based on Modbus, running at a speed of 1 Mbps and using a twisted pair physical layer. Unlike standard Modbus RTU/TCP, Modbus Plus uses a peer-to-peer token passing method, where there is no master-slave distinction on the network - each node can actively send data upon receiving a token.

⚠️Current StatusModbus Plus has been officially included in Schneider's phased out protocol. The new Schneider PLC product lines (such as M580, M340) have fully shifted towards Ethernet based communication methods such as Modbus TCP and Ethernet/IP. Unless you are maintaining an old Modicon Quantum system that is still running, there is no need to pay attention to Modbus Plus and SA85 drivers.

Modern alternative solutions

If you are building a new industrial control system, you should no longer use Modbus Plus and SA85 cards. Modern alternatives include:

Summary

SA85 Linux Driver is a historically significant open-source project that showcases the early application of Linux kernel drivers in the field of industrial communication. This driver played an important role in industrial control systems in the early 2000s, helping users connect Modicon PLCs in Linux environments. Nowadays, with the widespread adoption of Modbus TCP and industrial Ethernet, new projects no longer require the use of Modbus Plus networks and SA85 hardware. But for engineers who are still maintaining the old Modicon system, understanding the working principle of this driver still has practical value.