Omron plc junk values

Ltpriyank

Member
Join Date
Sep 2020
Location
Pune
Posts
24
Hello Everyone!!!
I have been using CP1E-N40DR-D PLC for my project and during the initial run there were some junk values in the PLC devices , so i cleared all the memory areas and the issue was resolved. But after 2 weeks when i again started the PLC there were again some junk values in the memory areas.

So is there any solution so that these junk values don't get stored in memory areas without clearing the memory areas again and again.

Thank you!!!
 
Junk values where? Something has to be writing the values in your program
 
Not used the later Omron stuff but it is possible to make it compatible with the IEC that areas of memory are reserved for compile time.
To make it compatible with the older direct addressing & symbolic some PLC's reserve physical areas of memory for global symbolic addresses & local variables. For example Mitsubishi do this, globals that have physical addresses have as in the older systems M & D areas (bits & Words), an example is M0-M799 & D0 to D799 however, M900 & D900 and above are reserved to be used at compile time Depending on if it is a global or local symbolic tag it wil be allocated at compile time but in the case of a local symbol it is possible it could be used again in a different block of code so that is why it is only valid in the local block, whereas the global symbolic one will only be used as that symbolic address,
As you can see below
The simple add instruction has two inputs, one is a local, the other is a global that has been assigned a physical address & the out result is a global symbolic only.
The compile result shows that the local & global symbolic addresses have been allocated in the 900 reserved area, the global that also has a physical address is D20 in the user area.
So if Omron do something similar then unused addresses may be populated with data even if they are cleared by formatting or clearing the memory.
As I said I have not used Omron for some years but it is possible.

Local_Global.png Globals.png Locals.png
 

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