The blocks that are available for Modbus communication with SIMATIC S7 are delivered with a unique block number.
If there are already blocks in the user program that have these block numbers, there is a block number conflict.
Please proceed as follows to avoid this conflict.
- You can rename the Modbus blocks that are called directly in the user program.
- You cannot rename the blocks that are called internally in the Modbus blocks. You have to re-wire those blocks.
The table below shows the Modbus blocks that you can rename or re-wire.
||Modbus block > rename
||Block called internally from the Modbus library > re-wire
||Block called internally from the Standard / SIMATIC NET library > re-wire|
|Modbus/TCP RED V1
|Modbus/TCP RED V2
|Modbus/TCP PN CPU
||FB103, FB104, FB105
|Modbus/TCP PN CPU Redundant
||FB913, FB914, FB916
|Modbus/TCP SENTRON PAC
|FB109, FB110, FB111
||FB99, FB103, FC99
(*) The EQ_STRNG block is only in older versions of the product.
(**) If both EQ_STRNG and AG_CNTRL are used by the Modbus blocks are used, then AG_CNTRL is already re-wired in the Modbus library. More information about this is available in the relevant product manual.
You must follow a specific order when re-wiring the blocks that are called internally in the Modbus blocks. Re-wire the blocks - if necessary - in the order listed.
- EQ_STRNG, AG_CNTRL, AG_(L)SEND, AG_(L)RECV, TSEND, TRCV, TCON, TDISCON
- Internally called blocks (FB106, FB107, FB1734, FB908, FB906, FB103, FB104, FB105, FB913, FB914, FB915, FB99, FB103, FC99)
- Remaining blocks
You do not have to re-wire all the blocks. Even if you re-wire only a few internally called blocks, you must nevertheless keep to the order given above. In this case, you leave out the blocks that are not re-wired.