So Machine 4.3 IO Mapping with M251 PLC

[Mtoto]

Hi All,

I'm having a challenge when adding New devices on the existing running configured IOs bus also configured with Modbus IO map, it shifted the Modbus IO Map downward on the register which will interfered with the Mapping i.e communication

Example:-

Input cards:-

Card 1 Range: %IW0

Card 2 Range: %IW1

Modbus Range: %IW2

When adding New card Modbus arrangement changes

Card 1 Range: %IW0

Card 2 Range: %IW1

Card 2 Range: %IW2 (New Card)

Modbus Range: %IW3

Please advise

[shanwaaz]

When adding a new device to an existing IO bus configured with Modbus IO map, it is possible that the new device's address is conflicting with the existing Modbus address range. To avoid this, you can try the following:

1. Change the address range of the new device: Most IO modules allow you to configure their Modbus address range. Try changing the address range of the new device so that it does not conflict with the existing Modbus address range.

2. Re-arrange the existing IO modules: You can also try re-arranging the existing IO modules to create a gap in the Modbus address range, where you can add the new device. For example, if the existing Modbus address range is %IW0-%IW2, you can move the second IO module to %IW3-%IW5, creating a gap between %IW2 and %IW3 where you can add the new device.

3. Use a Modbus addressing tool: There are software tools available that can help you manage Modbus addressing conflicts. These tools can scan the Modbus network and suggest the best address range for the new device to avoid conflicts with the existing Modbus address range.

It is important to ensure that the Modbus addressing scheme is properly planned and documented to avoid conflicts and ensure reliable communication.

[hardik]

When adding a new input card to an existing running IO bus that is configured with a Modbus IO map, it is common for the Modbus IO map to shift downward on the register, as you have described. This can result in interference with the mapping, which can cause communication issues.

One way to address this issue is to update the Modbus IO map to reflect the new card's address range. In your example, you would need to update the Modbus Range to start at %IW3 instead of %IW2.

Another option is to use a dynamic addressing scheme for the input cards. This would allow the IO bus to automatically detect and assign new addresses to the input cards as they are added, without the need for manual Modbus IO map updates. This approach requires that the IO bus and the input cards support dynamic addressing.

It is also important to ensure that the Modbus addressing scheme used for the IO bus and input cards is consistent with the Modbus addressing scheme used by the Modbus master device. If there are any inconsistencies, it can cause communication issues.

Overall, when adding new devices to an existing IO bus, it is important to carefully consider the impact on the IO mapping and Modbus addressing scheme to avoid communication issues and ensure proper functioning of the system.