Description
The blocks that are available for Mode 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.

You can rename the Mode blocks that are called directly in the user program.

You cannot rename the blocks that are called internally in the Mode blocks. You have to re-wire those blocks.

The table below shows the Mode blocks that you can rename or re-wire.
 

Product	Mode block > rename	Internally called block > re-wire
Modbus TCP CP	FB108	FB106, FB107
Modbus TCP Redundant	FB1733	FB1734
Modbus TCP Redundant V2	FB909, FB907	FB908, FB906
Modbus TCP PN CPU	FB102	FB103, FB104, FB105

Table 01

You must follow a specific order when re-wiring the blocks that are called internally in the Mode blocks. This order must be kept in particular when re-wiring the T blocks in the case of Modbus TCP PN CPU.

• T blocks
• Internally called blocks (FB106, FB107, FB1734, FB908, FB906, FB103, FB104, FB105)
• 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.