System Start-up Behaviour

Initial Operation

The PROFINET protocol is handled automatically by the PROFINET Communication Module and the PLC operation system. When the Communication Module is initialized in the proper way and the user application is running, the Communication Module and the bus become active.

No function blocks are needed for the cyclic process data exchange. The access to the send and receive data to the according operands range can be performed in the direct way. The access takes place either via operands or symbolic variables. Special PROFINET functions are realised by function blocks of the PROFINET Library.

IP assignment

After switching on the power supply of the PLC, the Communication Module assigns the IP-addresses (by means of DCP) to the IO devices. The IO device identification is done by the adjusted position of the switches for setting the device identifier.

Initialization

When the user application changes into the run mode, the configured IO devices are initialized. At this time, the IO devices get their configuration (and the configuration of possibly connected I/O modules) by the IO controller.

Then the configured devices are compared with the available IO devices and I/O modules of the real assembly. If the result of the compare is conformed, the IO devices get their configuration. Otherwise the available devices get their configuration and the failure is displayed with the error LEDs of the bus module. The error can also be displayed by using the diagnosis function blocks.

The Communication Module and the IO devices change into the cyclic process data exchange when the configuration transfer is completed.

If the configuration is not successful or the cyclic process data exchange between IO controller and IO device is broken (e. g. removing of the plug), both participant

• close their communication
• change their status into the initial condition
• try to build up a new connection.

This procedure has no influence on devices where the configuration was successful.

Because of that a replacement of a faulty IO device can be done without restarting the PLC. But you have to consider that the new device must have the same position of the switches for setting the device identifier like the replaced one and switch off the power supply of the device you want to replace.