6. Configuring the Gateway
6.11.3. Adding a Special Modbus Command
Apart from the standard Modbus commands covered in the previous chapter, it is possible to create two types of special Modbus commands: Modbus commands using the same template as standard commands and Modbus commands whose nature and frame content can be completely changed by the user.
6.11.3.1. Modbus Commands Based on Standard Commands
You create a command of this type from the “Select Command” window (see chapter 6.11.2 With a Generic Modbus Slave, page 70), by choosing “Add Command” from the “Command” menu. The window shown below appears. It shows the structure of the future command’s query and response frames, which will then be added to the list of available Modbus commands. This structure includes the standard elements, that is to say the “Slave Address”, “Function” and “Checksum” fields, described in previous chapters.
Please see chapter 2.12 Command editor in the AbcConf user manual, entitled AnyBus Communicator – User Manual for further information about creating standard Modbus commands. This manual can be found on the CD LU9CD1 : “ABC_User_Manual.pdf”.
6.11.3.2. Modbus Commands which Can Be Completely Changed by the User
In AbcConf, these commands are known as “Transactions”. Unlike in the previous case, the whole structure of the query and response frames associated with these commands correspond to an association of input or output data in the gateway’s memory (“Data” fields), constants in Byte, Word or DWord format and a final “Checksum” field.
All of the data contained in the query and response “Data” fields of a “Transactions” command are managed by the
N.B.: You must not place more than one “Data” field in any Modbus frame. This guarantees that all of the data involved will be processed by the gateway at the same time.
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