MVI56-MCMR Comm Fail Detection
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cjblake
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Wednesday 06 December 2006 10:35:08 am |
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MVI56-MCMR Comm Fail Detection
I am trying to implement logic for automatically detecting a comm fail between the MVI and Slave device. Do I need to periodically toggle the MCMRCmdExecute[0] in order to retrieve the module status? If so, then which is the appropriate tag to check for a failure. I want to know if I am not receiving data, i.e. has the cable been disconnected. I am trying to use the MCM.InStat.Prt1.CurErr but it does not seem to be consistent.
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jsanders
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Wednesday 06 December 2006 3:24:25 pm |
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RE:MVI56-MCMR Comm Fail Detection
The best way to monitor communications health on one of our Modbus modules when it is the Master is to Monitor the Command Error List. Please see the following posts for additional information:
http://www.prosoft-technology.com...rax/module_communication_error_codes
http://www.prosoft-technology.com...pport/bulletin_board/inrax/mvi56_mcm
http://www.prosoft-technology.com...mvi56_mcm_determine_the_slave_status
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cjblake
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Thursday 07 December 2006 5:31:35 am |
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RE:MVI56-MCMR Comm Fail Detection
Thanks for the reply. However, I believe the situation is different for the MCMR. The User-Defined data structures are different between the MCM and the MCMR. I still not understand if I need to perodically toggle the MCMRCmdExecute[0] bit in the first rung of the MSG_BLKS ladder routine.?? It appears that I do in order to get the Status from the module. I have been watching the different points in the Tag Database trying to determine what parameter will change when I disconnect and re-connect the cable to the slave device.
I appreciate your help.
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jsanders
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Thursday 14 December 2006 4:06:52 pm |
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RE:MVI56-MCMR Comm Fail Detection
Yes, there are some differences in the way the MCM and the MCMR bring in general module status information. In the MCM, the status is updated as part of every new Local:1:1.Data input image. To get the same information for the MCMR, you have to request it with the special MSG rung and you do have to toggle the trigger bit whenever you want it updated.
HOWEVER....
To get the best communication health information for either the MCM or MCMR module when the module is a Master, you would want to use the Command Error Pointer to put the Command Error List into your Read Data area, and hence it shows up in the ReadData array. The setup for this is the same for the MCM or the MCMR. This uses a different mechanism; and , therefore, does not require toggling the MSG in the MCMR.
If the MCM or the MCMR are being used as Slaves, you will have to resort to using the general Status information, already discussed.
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