The Allen-Bradley MicroLogix 1200

ML1200-FRONT-ON-WHITEIn the year 2000, six years after the MicroLogix 1000 launch and one year after the launch of the MicroLogix 1500, the MicroLogix 1200 was released into the market.

This new MicroLogix represented the lower end of Allen-Bradley’s second generation of Micro hardware, with the MicroLogix 1500 representing the higher end.

The 1200 was released in two I/O sizes: 24 and 40. But unlike the MicroLogix 1000, the MicroLogix 1200 supported from three to six 1762 expansion modules, the actual number depending on power consumption of the modules chosen.

ML1200-XIO-CONNECTED-2Unlike SLC-500 fixed units, the MicroLogix 1200’s expansion I/O was rackless, and interconnected by use of short ribbon cables. This was very similar to the older SLC-100 and SLC-150 expansion I/O, but the 1200’s I/O was considerably smaller.

The 1200 was programmed with the same Windows based RSLogix 500 software (version 4.0 or greater) that programmed the SLC-500, MicroLogix 1000 and 1500, but it could not be programmed with the MicroLogix 1000’s Hand Held Programming Terminal. This was likely done to allow for the addition of many advanced features which the handheld didn’t support. It was also very likely a nod to the fact that by the year 2000 the use of personal computers for programming automation devices had become commonplace in manufacturing.

As with the MicroLogix 1000, the MicroLogix 1200’s DC Input models supported either sinking or sourcing inputs. This was unlike SLC-500 I/O modules ML1200-RTBfor which you had to choose either sinking or sourcing. But, unlike the MicroLogix 1000, the MicroLogix 1200 came equipped with removable terminal blocks and wiring labels.

The MicroLogix 1200 did include the same Mini-Din RS-232 serial port for communications and porgramming (aka COMM 0) as the MicroLogix 1000 and 1500 base. However, Rockwell made a strange choice to make the opening for the cable smaller, thus requiring users buy new series C cables as the older and larger series A and B cables would not fit.

ML1200-COMM0-CABLEWhen it came to communication protocols, the six years between the 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. However, the 1200’s COMM 0 still only supported RS-232, so in order to communicate on DH-485 or Modbus using RS-485, a 1761-NET-AIC (and a Mini-Din to Mini-Din cable) was needed to convert RS-232 to RS-485.

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 COMM 0 port full ASCII Read/Write support. Then 8 months later Rockwell released the series C version which added (among other things) DF1 Half Duplex Master and Modbus RTU Master protocol support.

ML1200-COMM0Four 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.

ORSLOGIX-MICROver time, as Rockwell continued to expand it’s MicroLogix line, many customers began using the MicroLogix exclusively. However, new customers still had to buy the more expensive RSLogix 500 / SLC-500 programming software just to program the MicroLogix line. This became a sore point as that software was more expensive than many of the MicroLogix models themselves.

To address this, in 2008 Rockwell released a MicroLogix only version of RSLogix 500, RSLogix Micro, for $129. This was  a substantial savings over the cost of any version of RSLogix 500. Then a year later Rockwell released a free version of the same software for programming just the MicroLogix 1000 and 1100. It was named, “RSLogix Micro Strarter Lite.”

Today, even after 15 years and even with newer products that include Ethernet and Online Editing, the lower cost and high functionality of the MicroLogix 1200 has continued to make it one of Rockwell’s most popular MicroLogix Controllers for small systems.

If you would like to find out more about the MicroLogix 1200 you can visit the manufacturer’s product webpage HERE.


Shawn Tierney
Automation Consultant
Insights In Automation

Did you find my article helpful? Why not become a Premium Member with a small donation, and in return I'll give you a coupon for $10 of my automation downloads! Find out more here

The Automation School - PLC Basics - Article Banner

Leave a Reply