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Old March 15th, 2019, 07:16 AM   #1
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sellis4003 is offline
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ASCII code for Micrologix 1100

Hi Guys, i am reposting this beacuse I'm still having issues with the "READ" ARL or ARD instructions. I have a pdf of a program that I found on the Rockwell site that is slightly modified for the Write command but I can write fine. I would like to be able to read back commands that I just wrote to the device as well as solely just monitor certain ASCII data from the device. Cannot seem to read any ASCII from the device and not sure how to set up my string table for the reads. Any help would be much appreciated.

Hello, I am working with a micrologix 1100 allen bradley plc and I need to send and receive ascii code to a sensor device. The syntax for the commands that the manufacture states are the following:

set:LO=xxxx -(to set the low speed)
set:HI=xxxx -(to set the high speed)
I can get this to work using an AWA write command with a ACN command by typing the (set:LO=) in my ST string file and loading the xxxx variable from an hmi into and interger file and using an AIC command.
it works pretty well.

What I am having problems with is how to read information from the sensor.


I am not certain how I can read these with and ARL or ARD instruction.. Or do i need to do something else. I will also need to convert it back to an integer file.

Thank you for your time!!!

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File Type: pdf 1763_ML1100_ASCII_WRITE_READ 4 plc talk.pdf (19.0 KB, 18 views)
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Old March 15th, 2019, 10:30 AM   #2
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OkiePC is offline
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At first glance, it still looks a bit too simple to cover all your bases. It has been over ten years since I had to to ASCII with ladder logic, but when I did, I ended up with a state logic control over the steps and several places where I had my own timeouts and recover branches. I don't have access to that code or enough memory of the details to say much more.
It's not all the variables I am most concerned with, it's the undiscovered constants.
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Old March 18th, 2019, 06:38 AM   #3
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sellis4003 is offline
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Thanks for the reply Okie. Yes this is know this is too simple for what I am trying to do. I had some more complex code written with different time delays and more ASCII values that I needed to write and read but reverted back to this because I wasn't able to read anything back at all and thought I should start simple. I found this example on the Allen Bradley Website and Added the AIC and ACN for the write since I need to load the values from a touch screen. The writes all seem to work fine. I'm thinking it has something to do with the SYNTAX that the ASCII device is looking for. When I do a Write, I have to type a (set:LO=) into my string data file but not sure how to handle this for a read since the device is looking for a (get: LO=) to read a value. Any help would be much appreciated... Thanks again Steve!!!
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Old March 18th, 2019, 03:50 PM   #4
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shawn_75 is offline
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I think your scan time is beating out the very slow speed of the ARD. I'd separate out your AEX and ACI from the ARD. Use the ARD /DN bit to trigger the AEX and ACI.

Edit: I see that you need to write a get: command, then the device will respond with the value you want. If this is the case, I'd try to first clear the buffers, AWT your get: command, then test the buffer, then read. Give your AWT and ARD time to do their work as they can be quite slow. Trigger any concatenation off their /DN bits.

Last edited by shawn_75; March 18th, 2019 at 04:01 PM.
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Old March 19th, 2019, 06:13 AM   #5
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sellis4003 is offline
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Thank you Shawn for the quick reply. I appreciate your input, it certainly make a lot of sense. I was wondering if I had to do an AWT for the get as well. I will give these things a try and keep you posted.. Thanks again, Steve
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