User Manual

Communication
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11.1.3 Status of the communication interface
If the network interface is ready, this is indicated by the icon on the display.
The following conditions must be met for the network interface to be ready:
– Device start completed
– Network link established
– IP configuration valid
– Always true for static configurations
– True for dynamic configurations after the IP configuration has been received by the
DHCP server
The current status of the network interface can be viewed via the WBM, the display and
Modbus.
There are two LEDs on the RJ45 socket:
– Green LED for link status, to the left of the RJ45 connector
– Green LED for sending activity, to the right of the RJ45 connector
11.1.4 Security
The users are responsible for securing their networks against unauthorized access.
Up to four clients can access the interface simultaneously.
11.2 Modbus
11.2.1 Function
The Modbus protocol defines both a protocol on the application layer and a transmission
protocol. The application layer protocol is identical for all interface versions. The differences
between Modbus/TCP and Modbus/RTU lie in the transmission protocol.
On the application layer, Modbus supplies a 16-bit address space that can be used to ad-
dress 16-bit registers. Using various function codes, read and write operations can be per-
formed on registers.
For detailed information about the Modbus specification refer to
www.modbus.org/.
The EMpro supports the following function codes:
– 03 (0x03) Read holding registers
– 04 (0x04) Read input registers
– 06 (0x06) Write single register
– 16 (0x10) Write multiple registers
Here, it has to be noted that the device does not differentiate between holding and input reg-
isters. Both function codes return the same registers.