Download 6. Configuring the Gateway

6. Configuring the Gateway
6.12.3.2. User-Customizable Modbus Commands
In ABC-LUFP Config Tool, these commands are known as “Transactions”. Unlike in the previous examples
where many of the variables were fixed by the Modbus command selected, the whole structure of the query and
response frames associated with these transactions is dictated by data in the gateway’s memory. These data
fields in the gateway’s memory may contain constant and ranged values in Byte, Word or DWord format and a
final “Checksum” field.
(See Query’s table for details)
All of the data contained in the query and response “Data” and “Variable Data” fields of a “Transactions”
command are managed by the DeviceNet master, including the “Slave address” and “Function” fields if these are
placed in a “Data” field. For instance, this allows you to manage all of the Modbus frame fields from the
DeviceNet master if all of the query and response fields of a “Transactions” element (excluding “Checksum”) are
“Data” type fields, or “Variable Data” type fields for data with a variable data size (e.g. the Response to a Query
used to read a variable number of registers); see chapter 6.12.3.3, for a description.
WARNING
MORE THAN ONE “DATA” FIELD IN A MODBUS FRAME
Do not use more than one “Data” field per Modbus frame. Multiple “Data” fields in a single Modbus frame
may not be executed in the proper order by the gateway, leading to unintended consequences.
It is preferable for the master to set this data as only one “Data” field, even if this means that in-between
constants would become part of this “Data”, and thus be exchanged with the master.
Concerning “Variable Data”, there can be only one such field in any Modbus frame (Query or Response).
Thus, the “Add Variable Data” command of ABC-LUFP Config Tool will be disabled if the current frame
already includes a “Variable Data” field.
Failure to follow this instruction can result in death, serious injury, or equipment damage.
Constants in Byte, Word or DWord format place the values of these constants in Modbus query frames
(constants in “Query” elements) or compare them to the values located in the Modbus responses (constants in
“Response” elements). These comparisons are used to accept (identical values) or reject (different values) the
Modbus responses in the same way as for standard Modbus commands. The DeviceNet master does not have
access to these constants. They are mainly used to replace fields such as “Slave address”, “Function”, “Starting
Address,” etc.
Please refer to the section on “Produce/Consume Menu” in chapter 5.4.2 Transaction and in chapter 5.5 Frame
objects in the ABC-LUFP Config Tool user manual, entitled AnyBus Communicator – User Manual, for further
information about how to handle “Transaction” commands. This manual can be found on the
http:///www.telemecanique.com website: “ABC_User_Manual.pdf”.
The LUFP9 gateway’s default configuration includes two “Transaction” commands. These are aperiodic
commands used for reading and writing the value of a Modbus slave parameter (necessarily a TeSys U motor
starter with the default configuration). They are configured solely for the “TeSys U n°1” node, as the address of
the slave is controlled by the DeviceNet master via the first byte of the “Data” field, which corresponds to the
“Slave Address” field in standard Modbus commands. This allows the DeviceNet master to send this command
to all of the Modbus slaves, slave by slave, through the first byte of the “Data” field. The remaining fields of the
frames used by these two commands are also placed in the same “Data” field. So the DeviceNet master has
access to all of the content of the frames in these two commands.
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