Reading Modbus RTU Tags > 50,000

[andybdjuk]

Hi, i have been reading some 40000 range tags with no problems but i need to read 2 tags 57388 and 58389. I get invalid errors. How can i read these tags without upsetting everything else?

Thanks

Andy

[AzeoTech]

Are your 40000 range tags really 40000 (PDU or 0 indexed) or are they logical tags (i.e. start at 40,001 and translated to 0, 1, 2 in the PDU)? I'm guessing that they are logical tags, in which case your 50,000 tags really don't exist in logical space. So you have to do everything in 0 indexed mode. First, to lock it into 0 indexed mode you are going to have to read a 50,000 before any others. Then you'll probably find that all your 40,000 tags stop working because they will no longer be translated to 0,1,2 so you'll have to subtract 40,001 from each one to get them to work.

[andybdjuk]

Hi, stillproblems,

From the manual:

Regulation Voltage-

PDU Address = 0xE000

Logical Address = 57345

Battery Voltage-

PDU Address = 0x0008

Logical Address = 9

I put these in the Channel Table View in this order but still in command/alert shows P-ModbusRTU 0002 Illegal Data Address.

UMM stuck again

Thanks

Andy

[AzeoTech]

Well, the manual is still wrong. The logic address for a holding register like battery voltage with a PDU address of 8 is actually 40,009.

Anyhow, just use the PDU addresses, making sure to convert to decimal. E000 is 57344, so put that in the channel number. Use Read Holding U16 to start. If that doesn't work, do Read Input U16.

Also, make sure you don't have any channels in the 30,000 and 40,000 range. If you do, delete them, save your doc, and restart DAQFactory as those will put DAQFactory into logical notation, which as I've already said, is incorrect in your manual and so I think is what is confusing you.