GE instruction manual Basic settings, P485 scan list

COMMUNICATION MODEL

The P485 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 P485, the P485 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: P485 scan list

Basic settings

PARAMETER WINDOW 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 4–13for 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 P485 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 P485.

Due to its impact on subnet functionality, use caution when changing this parameter.

NOTE

5–2 P485 MODBUS TO PROFIBUS CONVERTER – USER GUIDE