modbus not working. it's giving erroneous value.
working on Modbus serial communication using MOD_COM_Mast. I have AC500 plc that needs to talk to three third party drives. I have to write& read from 1797,1798 ( drives Modbus address for speed ref and cw resp. for all three drives) and also only read from modbus address 2049(drive modbus address for speed feedback from three drives). I can read and write on 1797 and 1798 but can't read from 2049. I have attached the program for your reference.
I tried to consolidate three modbus address in single MOD_Com_Mast but the number of words that it can read is over the limitation, fc 3 can only do 125 words. I created a separate MOD_COM_Mast for modbus address 2049 but it overwrites in two of the first modbus address (1797,1798) and also when i am online it doesn't respond at all.
(1797-2049 is 253 words)
How do i resolve this issue.. need your help please.
I got advice from some of the folks but still not working.
Voted best answer
As you explained, you have to create 2 MOD_Com_Mast blocks but also TWO variables of type ARRAY (or one with a 2 fields for 1797,1798 and the other one only word) as an output of the blocks MOD_Com_Mast.
With the first MOD_Com_Mast read only 2 words (1797, 1798) and put them in ARRAY.
With the second MOD_Com_Mast read only 1 word (2049) and put it in the word (or in the first field of the SECOND array).
Then it will work perfectly !