In today’s article we’ll review the communication protocols supported by all the models and series of Allen-Bradley MicroLogix programmable controllers.
MicroLogix 1000 Protocol Support:
- Channel 0:
- Series A: DF1 Respond Only
- Series B: Same as series A
- Series C & Analog: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485
The MicroLogix 1000’s single serial port initially only supported the DF1 Protocol, and was limited to respond only mode. This meant the MicroLogix 1000 could respond to read and write commands from other devices, but it couldn’t initiate a request.
Later, with the introduction of the series C version of the MicroLogix 1000 discrete units (and 20 point Analog models) the MicroLogix 1000 gained the ability to initiate communications using DF1, as well as the ability to communicate using the DH-485 protocol.
MicroLogix 1200 Protocol Support:
- Channel 0:
- Series A: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, and Modbus RTU Slave
- Series B: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, Modbus RTU Slave, and ASCII Read/Write
- Series C: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem
- Prog/HMI Respond Only port
- Series C: Fixed at DF1 Full Duplex, 19,2K, CRC, No Parity or Handshaking
When it came to communication protocols, the six years between the launch of the MicroLogix 1000 and 1200 made a big difference. The MicroLogix 1200 was initially released with support for DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, and Modbus RTU Slave.
Not long after it’s initial release, Rockwell introduced the series B version of the MicroLogix 1200 along with RSLogix version 4.5. This release gave the MicroLogix 1200’s Channel 0 port full ASCII Read/Write support. Eight months later Rockwell released the series C version which added DF1 Half Duplex Master, Modbus RTU Master protocol, and DF1 Radio Modem support.
Four years after the original MicroLogix 1200 release, Rockwell upgraded the line by adding six additional models in 2004. These new models included a second, “Respond Only” communications port on the left side of the unit that was used for either programming or connecting an HMI. Models with the second port simply had an additional “R” (for Redundant port, or Respond only port) added to the end of their catalog number.
MicroLogix 1500 Protocol Support:
- LSP
- Channel 0:
- Series A: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485
- Series B: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, Modbus RTU Slave, and ASCII Read/Write
- Series C: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem
- Channel 0:
- LRP
- Channel 0:
- Series B: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, Modbus RTU Slave, and ASCII Read/Write
- Series C: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write
Channel 1:
- Series B: DF1 Full Duplex, DF1 Half Duplex Slave, DH-485, Modbus RTU Slave, and ASCII Read/Write
- Series C: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem
- Channel 0:
The first MicroLogix 1500 processor released, the 1764-LSP, had no communications port of it’s own. Instead, to connect a computer or HMI to a MicroLogix 1500 system the user 
would use the communications port built into the MicroLogix 1500’s I/O Base.
This I/O base communications port initially supported DF1 Full Duplex, DF1 Half Duplex Slave, and DH-485.
Then in the year 2000, Rockwell introduced the series B version of the MicroLogix 1500 along with RSLogix version 4.5. This release added Modbus 
RTU Slave protocol support as well as full ASCII Read/Write support.
Later in the year 2000, Rockwell released a second MicroLogix 1500 processor, the 1764-LRP. This new processor included its own communications port, Channel 1. But unlike the “respond only” port that is found on “R” models of the MicroLogix 1200, the MicroLogix 1500 LRP’s serial port was a fully functional.
The last addition came in 2003 when Rockwell released series C of the MicroLogix 1500. This release added support for DF1 Half Duplex Master, Modbus RTU Master, and DF1 Radio Modem protocols.
MicroLogix 1100 Protocol Support:
- Channel 0:
- Series A: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem
- Series B: Same as series A
Channel 1:
- Series A: Ethernet/IP (Messaging/Explicit,) BOOTP Client, DHCP Client, SNMP Server, HTTP Server
- Series B: Ethernet/IP (Messaging/Explicit,) BOOTP Client, DHCP Client, SNMP Server and Client, HTTP Server, duplicate IP address detection
The MicroLogix 1100’s Channel 0 serial port supports DF1 Full Duplex, DF1 Half Duplex Master or Slave, DF1 Radio Modem, ASCII, DH-485, and Modbus RTU Master or Slave.
The built-in 10/100 Mbps RJ-45 Ethernet port (Channel 1) supports Ethernet/IP peer to peer messaging, often referred to as CIP Explicit Messaging. Note: It does not support I/O connections or CIP Implicit Messaging.
The series A Ethernet Port supports Boot-P, DHCP, SNMP Server capabilities, as well as a built-in webserver used to monitor system status or access data table addresses via pre-configured webpages. The series B models added SNMP Client capabilities as well as duplicate IP address detection.
MicroLogix 1400 Protocol Support:
- Channel 0:
- Series A: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem, DNP3
- Series B: Same as Series A
- Channel 1:
- Series A: Ethernet/IP (Messaging/Explicit,) BOOTP Client, DHCP Client, SNMP Server and Client, HTTP Server, duplicate IP address detection
- Series B: Ethernet/IP (Messaging/Explicit,) BOOTP Client, DHCP Client, SNMP Server and Client, HTTP Server, duplicate IP address detection, Modbus TCP, DNP3 over IP.
Channel 2:
- Series A: DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem, DNP3
- Series B: Same as Series A
The MicroLogix 1400’s Channel 0 serial port supports DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII 
Read/Write, DF1 Radio Modem, as well as DNP3 Slave.
Unlike the 1100, the 1400 includes a second serial port (Channel 2.) This additional port supports DF1 Full Duplex, DF1 Half Duplex Master or Slave, DH-485, Modbus RTU Master or Slave, ASCII Read/Write, DF1 Radio Modem, as well as DNP3 Slave.
The 1400 also comes with an RJ45 10/100mbps Ethernet port (Channel 1.) This port supports Ethernet/IP peer to peer messaging, often referred to as CIP Explicit Messaging. Note: It does not support I/O connections or CIP Implicit Messaging.
The series A models support Boot-P, DHCP, SNMP Server and Client capabilities, as well as a built-in webserver used to monitor system status or access data table addresses via pre-configured webpages.
In 2010, Rockwell released the series B model which enhanced the Ethernet port adding Modbus TCP and DNP3 over IP. It also added the ability to disable incoming connecting, duplicate IP detection, and unconnected messaging.
I hope you find the above details about the MicroLogix’s supported protocols helpful.
If you have any comments, questions, or corrections please don’t hesitate to share them by using the “post a comment or question” link below.
Until next time, Peace ✌️
Shawn M Tierney
Technology Enthusiast & Content Creator
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Great work on this article – thanks for your efforts
Thanks Steve!
Have a great night,
Shawn