Which blocks for Modbus/TCP can you rename or re-wire when the block numbers of the Modbus blocks are already being used in the user program?
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. When re-wiring all the internally called blocks must be in the STEP 7 project, this means that you do not re-wire in the library, but you use the sample project for re-wiring.
The following table shows the Modbus blocks that you can rename or re-wire.
|Product||Article number||Modbus block > Rename||Block called internally from the Modbus library > Re-wire||Block called internally from the Standard / SIMATIC NET library > Re-wire|
up to V5
|Modbus/TCP CP V6||6AV6676-6MB00-6AX0|
|FB905||FB number cannot be changed:|
|Modbus/TCP PN CPU up to V2.6.1||2XV9450-1MB02||FB102||FB103, FB104, FB105||TSEND|
|Modbus/TCP PN CPU V3||6AV6676-6MB20-3AX0|
|FB900||FB number cannot be changed:|
|Modbus/TCP CP Redundant V2||2XV9450-1MB11||FB909, FB907||FB908, FB906||AG_(L)SEND|
|Modbus/TCP CP Redundant V3|
|FB909, FB907||FB908, FB906||AG_(L)SEND|
|Modbus/TCP PN CPU Redundant||6AV6676-6MB10-0AX0|
|FB917, FB915||FB913, FB916, FB914||TSEND|
|Modbus/TCP SENTRON PAC||6AV6676-6MA30-0AX0|
|FB109, FB110, FB111||FB99, FB103, FC99||TSEND|
(*) 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, 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.
Note on the Modbus/TCP PN CPU
If the T blocks are re-wired, the MODBUSPN block must have a higher number than the lower-level blocks.