PROFIBUS is EN 50170-compliant and enables communication between ET200 distributed I/O devices, HMI devices and numerous other field devices on the one hand, and the programmable controllers on the other. In addition, the entire automation system can be started up, tested and diagnosed via the field bus.

PROFIBUS is open for field devices of any manufacturer. Siemens supports connection of further field devices to PROFIBUS through open marketing of ASICs and interface modules as well as through technical consulting of manufacturers of components for PROFIBUS.

The integral fibre-optic interfaces of the ET 200 distributed I/O devices and the S7-400 enable problem-free installation of fibre-optic bus lines especially in environments subject to electromagnetic interference.

Operation

In a bus system, the bus nodes share the transmission medium. The bus access control defines when a bus node can have access to the transmission medium. PROFIBUS uses for this purpose a hybrid access mode (Token Passing with underlying Master-Slave). The access procedure differentiates between active bus nodes (masters) and passive bus nodes (slaves).

One active node at a time receives transmission rights (token) giving it access to the bus. After a specified time has expired, this node passes the token on to the next active node on the bus system. If any node does not wish to transmit, the token is passed immediately to the next master module.

Passive nodes such as ET 200 distributed I/O devices do not receive transmission rights. They are accessed direct by the master module to which they are assigned.

Configuring

There are helpful and easy-to-use tools available to the user for configuring, parameterisation, startup and diagnostics of the PROFIBUS-DP field bus system.
The STEP7 programming software is used for the master interfaces of the SIMATIC S7. With SIMATIC S7 and PROFIBUS-DP, programmable controllers are merging more closely with the field technology. All the functions required for configuring the field bus system are already integrated into the STEP programming software.
The COM ROFIBUS parameterisation software is used for SIMATIC S5 master interfaces. It enables easy, menu-driven parameterising of the PROFIBUS-DP field bus with a SIMATIC S5 master and the IM308-C interface module as well as with the S5-95U/DP master programmable controller.

The following table shows which interface modules and communications modules are available for connection of the PROFIBUS-DP field bus.