1) How many calls are there to DB4?

2) Are those DB4 calls all scanned / enabled in the same scan cycle?

3) Any specific reason for using REAL numbers?

Do a small test and have only one call to the modbus master instruction. What result do you have?

I don't know the function block "Modbus_Master", but it seems to be the wrong adresses. I think, you have to use the Modbus Protocol Start Adress 16#002A (dec 42) and 16#002C (dec 44). Depend on the beginning address 0 or 1 it maybe required an offset of 1. The address registers beginning with 40000 marks the holding registers, then subtract 40000 and you get the modbus register with offset +1.

Regards, Scorp

 Hi. as far as I am concerned, I think you mean that how many different labels(for MODBUS_MASTER block). All the blocks have the same data block name and I have a lot of them working perfectly so far.
There is a counter which activate the DB4 calls in sequence.
There is no specific reason to use Real. I used all the data types available just to make sure the operation is interrupted due to another reason. I hope I was clear regarding your questions. Thank you and waiting for your feedback.

#dP

1) How many calls are there to DB4?

2) Are those DB4 calls all scanned / enabled in the same scan cycle?

3) Any specific reason for using REAL numbers?

Do a small test and have only one call to the modbus master instruction. What result do you have?

MIDO101

All the blocks have the same data block name and I have a lot of them working perfectly so far.
There is a counter which activate the DB4 calls in sequence.

Please show me. (There is a problem nagging at me - but I need to see the bigger picture before making a public statement.)

Did you try yet to make a small program that has only ONE instruction (MODBUS_MASTER with DB4) call? This is just a sanity check to ensure that you do actually get data from the address as you have it.