GE D485, Instruction Manual

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5–2 D485 MODBUS TO DEVICENET CONVERTER – USER GUIDE
COMMUNICATION MODEL
The D485 uses pre-configured Modbus RTU commands, acting as a Modbus RTU master.
With Modbus RTU, each transaction is substituted with a pre-defined command that can
be selected from a list of available commands.
It is still possible, though, to define custom message frames by creating a transaction
instead of selecting a pre-defined command. A command is actually a transaction that
has been defined in advance and stored in a list.
SCAN LIST
Once the configuration has been downloaded to the D485, the D485 firmware searches
the scan-list, using the defined transactions for communication with the slave-devices.
Each node in the scan-list represents a slave device on the Modbus network. In EnerVista
P485/D485 Setup, each node is given a specific name and assigned an address in standard
Modbus RTU commands. The address must match the internal setting on the slave device.
Figure 5-2: D485 scan list
Basic settings
NETWORK SETTINGS
Select ‘Modbus Network’ in the Navigation window to gain access to basic settings in the
Parameter window.
Figure 5-3: Parameter window
COMMUNICATION
Refer to Serial interface settings on page 4–13 for details.
MESSAGE DELIMITER
The message delimiter value is the minimum time in steps of 10 ms separating the
messages. According to the Modbus specification, the message delimiter has a default
setting of 3.5 characters.If this value is set to “0”, the D485 will use the Modbus standard
3.5 character message delimiter. The time in milliseconds is then dependent on the
selected baud rate, but this is all handled by the D485.
Due to its impact on subnet functionality, use caution when changing this parameter.
NOTE