What Protocol Does the Allen Bradley MicroLogix 1400 Use?

Introduction

The Allen-Bradley MicroLogix 1400 is one of Rockwell’s most versatile compact PLCs, known for combining flexibility with strong communication features. Unlike earlier MicroLogix models, which had limited connectivity, the 1400 includes built-in Ethernet and expanded serial ports, making it far easier to integrate with modern systems.

In automation, communication protocols are what allow machines, controllers, and monitoring systems to “talk” to each other. Without them, devices would operate in isolation. The MicroLogix 1400 shines here—it supports multiple protocols, enabling smooth integration not just with Rockwell hardware but also with third-party devices, making it a reliable choice for connected industrial environments.

Overview of MicroLogix 1400 Communication

One of the key features of the MicroLogix 1400 is its built-in communication ports. At the heart is an Ethernet port, not found on earlier MicroLogix models. This RJ-45 port is 10/100 Mbps Ethernet and allows for fast and reliable data transfer across the plant network. Along with Ethernet the controller has two serial ports: one isolated RS232/RS485 combination port and one non-isolated RS232 port. These ports allow you to connect to older devices that still use traditional serial communication.

Also the MicroLogix 1400 has a USB port. While this port is mainly for programming and diagnostics not for industrial protocol communication, it’s nice to have for the engineer on site. The combination of Ethernet, serial and USB makes the MicroLogix 1400 a bridge between legacy systems and modern Ethernet based architectures.

The value of supporting multiple protocols can’t be overstated. Many plants have a mix of new and old equipment and not all devices use the same communication method. A controller like the MicroLogix 1400 that supports both Ethernet based and serial based protocols gives you the flexibility to connect older devices without sacrificing compatibility with modern networks. This way the PLC can be a long term investment that can adapt to the evolving plant requirements.

Supported Communication Protocols

EtherNet/IP

The best feature of the MicroLogix 1400 is the built in Ethernet. The Ethernet port supports EtherNet/IP, Rockwell’s standard Ethernet based industrial protocol. 10/100 Mbps speed allows for fast and reliable communication with other devices on the network. EtherNet/IP makes it easy to connect the PLC to SCADA systems, HMIs and other Rockwell controllers for peer to peer messaging.

In addition to EtherNet/IP the MicroLogix 1400 Ethernet port also supports Modbus TCP/IP and DNP3 over IP. Modbus TCP/IP is an open protocol used to integrate devices from different manufacturers, so it’s great for connecting the MicroLogix to third party equipment. DNP3 is used in industries such as utilities and energy where reliable structured data exchange is critical. These additional options make the MicroLogix 1400 much more versatile than controllers limited to Rockwell only ecosystems.

In modern plant networks Ethernet based communication is a must. With more factories adopting Industry 4.0 practices the ability to connect controllers directly to IT networks is key. The MicroLogix 1400 with Ethernet has this connectivity built in.

Serial Protocols (RS232/RS485)

While Ethernet is the future, many industries are still stuck in the serial past. The MicroLogix 1400 has both an isolated RS232C/RS485 port and a non-isolated RS232 port so you have maximum flexibility for serial connections.

Through these ports the controller supports:

• DF1: Rockwell’s protocol used for point-to-point communication, programming and device-to-device communication.
• DH-485: Allen-Bradley’s networked protocol for multiple devices to communicate on the same network.
• Modbus RTU: A widely used open protocol for instruments, drives and other industrial devices across vendors.
• DNP3: Important in utility, water and energy sectors, DNP3 is a secure and structured protocol often used in SCADA systems.
• ASCII: A flexible protocol for string based data, useful for custom devices and simple data transmission.

So the MicroLogix 1400 can work in a wide range of environments, from legacy plants with decades old equipment to newer facilities that still use serial networks at the device level. With both isolated and non-isolated ports the PLC provides safer and more reliable connections in noisy environments.

USB

And finally, the MicroLogix 1400 has a USB port. Unlike the Ethernet and serial ports, the USB port is not for industrial communication protocols. It’s for programming, configuration and diagnostics only. Engineers can use it to upload or download programs quickly or troubleshoot during commissioning.

While limited in use, the USB port is another convenience for users during setup and maintenance. It makes it easier to connect laptops or programming devices without needing special cables or adapters.

Why Multiple Protocols Matter

One of the biggest advantages of the MicroLogix 1400 is its ability to handle multiple communication protocols at once. In most plants, equipment is a mix of old and new—some machines still run on Modbus RTU or DF1, while newer ones rely on EtherNet/IP or Modbus TCP. Instead of using extra gateways or adapters, the MicroLogix 1400 can talk to all of them directly, making integration much simpler.

This flexibility means the PLC works seamlessly with both Rockwell equipment and third-party devices. For example, it can connect to an HMI over EtherNet/IP while also communicating with a variable frequency drive via Modbus RTU. That kind of versatility keeps operations running smoothly, even as system requirements change.

Another key benefit is remote access. With Ethernet and support for protocols like DNP3 over IP, operators can monitor, troubleshoot, and collect real-time data without being on-site. This is especially valuable in industries like water treatment, utilities, and building automation where downtime is costly and remote visibility is essential.

In short, the MicroLogix 1400’s protocol support gives businesses the flexibility to manage today’s mix of technologies while staying ready for tomorrow’s upgrades.

Summary Table of Protocols

Conclusion

The Allen-Bradley MicroLogix 1400 stands out as a compact PLC that blends the best of both worlds—supporting legacy serial protocols like DF1, DH-485, and Modbus RTU, while also offering modern options such as EtherNet/IP and Modbus TCP/IP. This flexibility makes it easy to connect with both Rockwell and third-party devices.

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