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Allen Bradley Micrologix 1100 First Experience

This quite possibly could be the first article I ever wrote.  While it was written back in early 2006, it still holds some good insight into the Micrologix 1100 and the newer Micrologix 1400.  It used to have some crummy pictures that went with it, I may see if I can dig them up sometime.

I know there have been several of us contemplating whether or not to use the Micrologix 1100. I have finally got an application to use one on and I thought I would share my first impressions with you.

First here is a little background on the machine. I built the controls for the machine about 4 years ago using a Micrologix 1200. It has 4 expansion I/O modules, two 1762-IW16s, one 1762-OW16, and one 1762-IF2OF2. It uses one high speed counter (Input 0 and 1) hooked to an encoder and uses the 1762-IF2OF2 to control a AB 2098-DSD-020 servo drive. It uses a Panelview 600 DF1, 2711-T6C16, as a HMI.

I was asked to make some upgrades to it that was going to push the data memory over the Micrologix 1200s 2k limit. It was also to be hooked to the Ethernet network for data acquisition. I probably could have used a memory module and some 1761-NET-ENIs to do it but it seemed like a perfect time to try the Micrologix 1100. This was a much cheaper solution but the machine could only be down twice for a half a day each time. All other program changes would have to be made in 2 minute openings when new parts were being loaded. So not only did this test the capabilities of the Micrologix 1100 but also how easily it could be swapped for a Micrologix 1200.

I/O – There are some things you need to watch out for when planning to upgrade to a Micrologix 1100 or designing a new project for that matter

  1. There is only 10 inputs and 6 outputs on the Micrologix 1100 compared to the Micrologix 1200s 24 inputs and 16 outputs. I got lucky on this one. Most of the Outputs went through the expansion modules and I had enough spare inputs on the IQ16s to move all of the inputs to the expansion module. In the end I only had the encoder on inputs 1 and 2 and used five of the base outputs.
  2. BIG WARNING – The Micrologix 1100 only supports 4 expansion modules compared with the Micrologix 1200s 6 expansion modules. I had some other questions for Rockwell and tech support did inform me of this when I was talking to them. Lucky for me, I had exactly 4 expansion modules.
  3. The analog inputs are only 0 to 10 VDC and you can’t configure the data format like you can with the 1762-IF2OF2. 

    Program Conversion

At this point I converted the Micrologix 1200 program to a Micrologix 1100. It went very smooth but it erased my expansion module including their configuration and set my input filters on inputs 0 and 1 back to their defaults so the HSC function file would not count. After making some changes I needed to put the program back into to do some testing with the existing Micrologix 1200 and ran into some problems during the changes and testing.

  1. Message configuration. I already had some messages that were used on Micrologix 1200s through 1761-NET-ENIs to do the exact same communications so I started with them as a base.
    • I changed the message to go through channel 1 and I found I could not figure out how to the message path.
    • So I went to the instruction set help and selected message and there was no documentation apparently added for the 1100. Then went to the find tab of the help dialog and put 1100 in and there were the instructions for configuring the 1100 Ethernet message. I guess Rockwell forgot to put a link to it in the message help area.
    • There is a new data type, ROUTING, for configuring your path.
  2. Converting a 1100 program back to a 1200 program – I needed to test some of the new code and converted the 1100 program back to a 1200 program and ran into a flaw in RsLogix 500.
    • It erased my expansion modules and set my input filters back to default.
    • After the conversion I could not get the program to verify. In routine 20, rung 20 for instructions 1 and 2 it said "ERROR – Instruction not allowed on last rung." The rung only had a simple NEQ statement and a MOV statement that was all that was in it.
    • Also there were 22 rungs in the routine which means that rung 20 wasn't event the last rung.
    • After about an hour of looking at it, I realized that my Ethernet message instruction was on rung.
    • I viewed the configuration of the message and it had reverted to an acceptable message instruction. But when I tried to cut the rung out of it RsLogix 5000 came up with a memory error and crapped out. After several tries and I don't remember the final method I got the message instruction out of it and the program verified fine. I created a message instruction with the exact same parameters and it still verified fine.
    • So when you are doing your conversion and need to test on the old controller do not convert your program back to a 1200 program. Use two programs and copy/paste your rungs back and forth.

Then the new Micrologix controller came in. Here are some comments on the physical package.

  1. The inputs are grouped in a very similar way to the 1200 only less of them. I like this layout.
  2. All 6 outputs are individually isolated. This is a very nice improvement. Since I think Rockwell designed this to mainly use the expansion I/O you can use these 6 outputs for that odd voltage or different circuit configuration you need to turn on.
  3. The display doesn't do a thing for me. I don't like people having to open a panel unless something is broke and if they need to view something or change a setting there should be a touch screen on the machine. Plus the display is too small to really do anything with but it's there and I guess it looks neat.
  4. The communications ports come out of the side of this controller which is different than the 1000, 1200, and 1500. I had stated this concern in earlier post and after seeing the unit I still don't like it. If you mount the 1100 at the minimum left clearance (2 inches) it is very hard to deal with the Ethernet connector. Remember this is a conversion from a 1200 so changing the panel layout wasn't an option. I use Beldin 7919A shielded Ethernet cable which is very stiff so you can't bend it like a normal patch cable. You really need a compact 90 degree Ethernet connector.
  5. The 1100 is 2 inches narrower than the 1200 which was good for a conversion. That is where I got the clearance to put the Ethernet connector on it. I have to admit I cheat on the left clearance. There is usually a piece of wire duct right beside it so I cram it against the wire duct to save panel space and let it vent through the wire duct. The wire duct is plenty large so the controller still gets plenty of ventilation with the wires in the duct.
  6. There is a warning below the communications connectors that kind of scares me. It states "ATTENTION: Do not connect the RS-232/RS-485 Combo port directly to any other MicroLogix controller Channel 0 (RS-232) port or the 1747-DPS1 Port Splitter network port. Doing so will cause permanent damage to the comm. Port on the MicroLogix 1100".
  7. The +24VDC and 24VDC common are reversed from the Micrologix 1100.  This was the only problem I ran into during the installation.

Power up for bench testing

  1. It is very nice being able to make online edits. Of course PTO, PWM and MSG instructions can't be edited online and the first thing I need to edit is that message instruction I guessed at. But you couldn't do it in any of the other Micrologixs either. This includes editing anything else in the rung containing these instructions.
  2. There is a problem with an Ethernet message instruction after a power cycle if the Ethernet cable is not connected.  The port is in an inhibited state until it is hooked to the Ethernet network.  Also the IP Address can’t be view from the front display until it is hooked to the Ethernet network.  So if you are unsure of the address or want to change it before it is hooked to the network, you will have to go through the serial port.
  3. Ethernet communications performance is tremendously improved. I really thought they had crammed some type of serial to Ethernet adapter in it and it would be similar to a 1761-NET-ENI but it isn't.
      1. Message instructions – 90 ms
      2. Message instructions – 162 ms
      3. Message instructions – 208 ms
      4. Message instructions – 271 ms
      5. Message instructions – 328 ms
      6. Message instructions – 401 ms
      7. Message instructions – 446 ms
      8. Message instructions – 551 ms
      9. Message instructions – 607 ms
      10. Message instructions – 695 ms
      11. Message instructions – 787 ms
      12. Message instructions – 826 ms
      13. Message instructions – 905 ms
      14. Message instructions – 948 ms
      15. Message instructions – 1006 ms
      16. Message instructions – 1136 ms
      17. Message instructions – 1204ms
    • I did a test using multiple messages to the same controller using a Micrologix 1200 connected to Ethernet with a 1761-NET-ENI, a Controllogix L55M12 going through an ENBT and the Micrologix 1100. The 1200 took approximately 16.8 seconds to cycle through all of the messages. The Controllogix took 1.7 seconds. The 1100 too approximately 3.1 seconds. I think that is a tremendous improvement even though it is not as fast as the Controllogix response time.
    • I did some additional testing on the number of messages and the amount of information that can be read by Micrologix 1100. All of our messages are read messages so it did not test its ability to write messages. The communications setup for each message was the Micrologix 1100 reading data from a Controllogix 1756-L55M12 going through a 1756-ENBT. The data type was a long integer and the number of elements was 20 for each message. This is very similar to our normal setup so did not play with varying the element size to increase throughput. A one second response time was the maximum I wanted. According to the data I gathered the maximum number of messages that can be fired in this setup is 15 and the maximum amount of data that can be sent in one second is 1200 bytes. Below are the response times of the messages
    • Also in comparison to a SLC 5/05 - According to AB manual 1763-um001A-EN-P page F-2 optimum performance from a Micrologix 1100 to a Micrologix 1100 compared to AB manual 1747-um001A-EN-P optimum performance from a SLC 5/05 to a SLC 5/05 it looks like the Micrologix 1100s max is 11 messages at 100 words each for 2200 bytes per second. The SLC 5/05s max is 31 messages at 256 words for 15872 bytes per second. Both it appears in a perfect world with no other devices on the network
  4. The Micrologix 1100 does not have LED indicators like the other Micrologix do. You have to go to the I/O States Screen on the front of the controller to view the indicators. They are much harder to see than the LEDs. Usually you can tell which point is on from at least 4 feet back. You can't do that with the 1100 unless you have really good eyes.  Here are a few sample pictures.

  5. You can't go through the Ethernet port in and out on the DF1 port to download like you can in the Logix5000 platform. But for the cost I don't think that is something to grip about.

Overall I am going to say that the Micrologix 1100 is a great addition to the Micrologix family. Below is a summary of what I think the pros and cons of Micrologix 1100 are. I am listing more cons than pros but my cons are very minor compared to the improvements they have made.


  1. Ethernet communications – The communications performance is a tremendous improvement over a Micrologix 1200 going through a 1761-NET-ENI.
  2. All 6 outputs are individually isolated.
  3. Overall nice layout. Since it is a little smaller than the Micrologix 1200 it makes it very easy to upgrade.
  4. Uses the same expansion modules as the Micrologix 1200. Not only does this make upgrading from the Micrologix 1200 to the Micrologix 1100 very easy, but people are already familiar with the 1762 expansion modules and you do not have to worry about stocking spare parts for a whole now style of PLC.
  5. Built in Real Time Clock. But you must remember it has a battery so you will need to setup a battery replacement schedule.
  6. This is really a con but I think Rockwell handled this in the best way possible. When converting from one processor to another it is a pain that it erases your expansion modules. I can understand it taking the I/O configuration of the base unit back to the defaults since the I/O layout is different, but since the Micrologix 1100 and 1200 use the same expansion I/O it should be able to keep the expansion module configuration. This is probably done this way because the Micrologix 1000 can’t have any expansion modules and the Micrologix 1200 and 1500 use different styles of expansion modules. Plus the issue with the Micrologix 1100 only being capable of 4 expansion modules compared to the Micrologix 1200s 6. This may be the best way to have this so programmers will have to go configure the modules and realize that there are only 4 that are configurable.
  7. Online Edits. Boy have I missed this.
  8. Increased message buffers compared to a Micrologix 1200 through and 1761-NET-ENI.
  9. Data Logging – I don’t think I have any use for this but am not sure exactly how you are supposed to apply this feature. RsLogix 500 help file is not clear on the use of this feature.
  10. Recipes – I don’t use recipes but I have heard others requesting this feature.
  11. With the Micrologix 1200 you had to either memorize the wiring diagram or take the covers that guard the I/O terminal screws off. When the covers were hinged up you so you could connect the wires you couldn’t read the labels that identified what each point was. The Micrologix 1100 does not have these covers. The terminal points are recessed into the plastic and the labels can be clearly read.



  1. The Ethernet port comes out of the side of the PLC. Need to find a 90 degree Ethernet connector for it. It is not a problem with standard Ethernet cable but when you go with a thicker cable like Beldin 7919A it is very hard to deal with the cable. Also this makes the Ethernet indicators below the connector very hard to see. Our basic technicians use these indicators to determine if there is something wrong with the physical hardware going to the unit.
  2. The display is too small to be functional and you should not have to open the panel to make adjustments or diagnose a machine.
  3. No LED indicators. The Micrologix 1100 uses the display to show the I/O and status of the PLC. From a cost standpoint I am sure this was much cheaper but you have to stare right at it to be able to see them. Many plants require windows in panel in front of the PLCs so the I/O and status LEDs can be seen without opening the panel. You won’t be able to see them through the Plexiglas with the Micrologix 1100.
  4. Lower amount of built in I/O. The Micrologix 1100 has 10 Inputs and 6 Outputs compared to the Micrologix 1200’s 24 Inputs and 16 Outputs. This will make planning for an upgrade a little more difficult.
  5. Lower expansion module capabilities. The Micrologix 1100 can only handle 4 expansion modules compared to the Micrologix 1200’s 6 expansion modules. Especially with the lower number of base I/O this will keep many Micrologix 1200 system from being able to be upgraded to an 1100.
  6. The analog inputs are only 0 to 10 VDC and you can’t configure the Data Format. When you are used to using the 1762-IF2OF2 this is a big difference. Plus in my first situation with the Micrologix 1100 I needed 4 analog inputs. So I used the 2 built in analog inputs and 2 analog inputs off of a 1762-IF2OF2. Even if they have to be 0 to 10 VDC only you should be able to change the data format. This may be in the generic configuration but I couldn’t find it.
  7. No I/O messaging. This is a complaint from a Controllogix point of view. For those of you who do not know, in Controllogix you can setup PLCs on a network so they pretty much become an extension of the Controllogix chassis. You can then use Produced and Consumed tags to communicate between the PLCs without message instructions. Managing messages in Controllogix becomes a pain after about 16 and the absolute limit is 40. Using I/O messaging the limit is well over 100. No other Micrologix has this ability either but it would have been a nice improvement.
  8. Instructions for configuring the Micrologix 1100 message instruction need to be clearer in RsLogix 500. Especially when it comes to the new Routing data file.
  9. Need to fix the bug in RsLogix 500 pertaining to converting from a Micrologix 1100 back to a Micrologix 1200 when using messaging.  Also the error in the verification of the program did not point to the rung that had the message instruction.
  10. The Ethernet port does not respond on power up until it is hooked to a switch. This includes viewing the IP address on the front display. If you aren’t sure what the IP address is and don’t want to hook it to the network until you find out, you are either going to have to hook it into a switch that is not connected to the network or pull out your serial cables and connect to the Micrologix 1100 through channel 0.
  11. Though I understand not being able to edit PTO, PWM, and MSG instructions while online, you should be able to edit other instructions in a rung containing one of these instructions.
  12. Inability to do multi-hop messaging from one Ethernet network to another Ethernet network.
  13. Although this is apparently a problem with all SLCs and Micrologixs, I wish the clock could be set from inside the ladder. I am used to the Logix5000 processors that let you set the clock with a SSV instruction. With the SLC and Micrologix, you must use the RTA instruction which either rounds up or down the seconds. Another controller must send a message to these to set the clock. One more message to handle the buffers on.
  14. No pass through from the Channel 1 Ethernet port to the Channel 0 Serial port. For the cost of the unit, I don’t think we can complain about this but it never hurts to wish.
  15. The built in web server needs to be more like the 1756-EWEB to be functional.  Simply being able to view data files is not useful.  Need to be able to create custom web pages.  Also, once you are communication to and from the Micrologix 1100 with message instructions, the web server becomes very slow to respond.