beijer exter T70 Modbus comms

brendanjlee

Member
Join Date
Dec 2007
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Brisbane
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Hi there,
I have been working on a project using a small embedded controller called a SPLat (www.splatco.com) with a Beijer Exter t70 HMI. I have modbus working and I am able to turn bits on and off, read bits in and write byte and word data to the SPLat however when I try to read word data back out from the SPLat I get strange results. It seems that the Beijer is reads the address at double the RAM location from where it should. It's odd because I've created an input box that displays the values I type in. When I input the data it definetely goes into the correct RAM location on the SPLat however when it reads the data back and updates the numeric indicator it's the wrong data.
I know that it's not the SPLat feeding the wrong data back as I have had it connected up to the PC directly using MBTestPro and was able to verify that it gives back data from the requested address so it must be a problem with the protocol the exter is using.
Has anyone got any ideas?????
Thanks,
Brendan
 
I'm not sure what you mean. If you mean a static offset then no as when I read 40000 I get correct data. When I read 40002 I get the data that's in 40004 and when I read 40004 I get the data in 40008 although in each case, when I write those addresses, the data goes into the right place.
Hope that helps.
 
Why your "reads" are 4 registers long?
It seems that there's a pattern there.
Do they have to be 4 registers long?
Could it be the way the controller is setup to do reads?
 
Some possibilities:

1. The Beijer HMI has options for addressing modes: single-word, double word, tripple-word, and it is set for more than single-word addressing.

2. The indicated address is not the one being read, but the next one available.
 
Lancie1 said:
Some possibilities:

1. The Beijer HMI has options for addressing modes: single-word, double word, tripple-word, and it is set for more than single-word addressing.

2. The indicated address is not the one being read, but the next one available.
I agree with Lancie.
It may be a setup issue on the HMI.
Though you do have an established pattern so far.
4 registers long for each "read".
I would look into that.
 
I'm talking about individual reads. I am doing single reads and getting the wrong data back. Why would it read incorrectly when it is writing correctly???
 
Lancie1 said:
Some possibilities:

1. The Beijer HMI has options for addressing modes: single-word, double word, tripple-word, and it is set for more than single-word addressing.

Is anyone familiar with the Beijer Exter HMI's? Do you know if this is an option? I have scoured the settings and can't find anything relating to this.
 
I haven't worked with Beijer HMIs but this is a common option on most of the ones I have worked with.
All HMIs are based upon a "tag" (Internal or externa;)which you have to define as the "type" of.
Boolean, word, double word, etc.
 
Hmmm.
I cannot seem to find any option to change that. What I don't understand is that to receive the data it is displaying it actually has to request an incorrect address. Thanks for your help anyways. I'll just keep plugging away at it.
 
Yes I am able to read single byte information and it is fine. Just not word information which is no good as I need to input and display integers.
 
Probably not the case but is there any word swapping and such? High word first Low word after it?
I'm clueless.
As Lancie said, maybe the address you do "read" is not the actual address but a different one.
The only thing that bothers me is the 4-register pattern.
It seems that there's a pattern that will lead me to some sort of "offset" either in the controller or the HMI.
 
...Just not word information which is no good as I need to input and display integers.
Word information normally would use a different "tag" than single bit information. Somehow the HMI must know how long each data string is. What value you get back depends ONLY on the starting point and the length of the data. Different lengths of data (all starting at same bit) can appear to be errors, until you figure out what you are seeing.
 

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