Explicit messaging can be used more effectively instead of implicit messaging in a few use cases. E.g. polling multiple services devices connected through a Modbus TCP to serial gateway; or configuring event-based read/write communication instead of cyclic ones.
EcoStruxure Control Expert provides many function blocks for explicit messaging. The Data_Exch block stands out as it allows to program any Modbus or Ethernet/IP query required by the users. However, from its user manual, it's not so clear on how to go about it.
This article can be read as additional guidance to users apart from the block's user manual. Focus is on using this block for any Modbus query, and as an example, Function codes 22 and 23 are implemented.
Usage of Data_Exch over Ethernet/IP is not included as it has been well described in an existing document.
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