PLC Siemens S7-400

CPUs

There is a graded range of CPUs from the entry-level CPU right up to the high-performance CPU for configuring the controller. All CPUs control large quantity structures; several CPUs can work together in a multicomputing configuration to boost performance. Thanks to their high processing speed and deterministic response times, the CPUs enable short machine cycle times.

The different CPUs are distinguished by, for example, work memory, address range, number of connections and execution time. As well as the standard CPUs, there are also two failsafe and three fault-tolerant CPUs available.

Signal modules

Signal modules are the interface of the controller to the process. A host of different digital and analog modules provide exactly the inputs/outputs required for each task. Digital and analog modules differ as regards the number of channels, voltage and current ranges, electrical isolation, diagnostics and alarm functions, etc.
However, the S7-400 signal modules are only a subset of the modules that can be connected to the S7-400 via PROFIBUS DP. Centrally connected signal modules can be connected and disconnected during operation. This makes module replacement extremely easy.

Function modules

The multi-facetted module range of S7-400 allows modular customization to suit the most varied tasks.
Apart from the CPUs with integrated functions and interfaces, there is a wide range of special modules in S7-400 design for technology.

Communication processors

Communication processors are used for connecting S7-400 to the different bussystems / communication networks as well for point-to- point link.

Point-to-point connection
Point-to-point link via communications processors (CPs) is an extremely powerful and low-cost alternative to bus systems. The advantage of point-to-point links over bus systems is especially pronounced when only a few (RS 485) devices are to be connected to the SIMATIC S7.
The CPs can also easily link third-party systems to the SIMATIC S7. Thanks to the great flexibility of the CPs, different physical transmission media, transmission rates or even customized transmission protocols can be implemented. For each CP, there is a configuring package on CD with electronic manual, parameterization screen forms and standard function blocks for communication between the CPU and the CP. The configuration data are stored in a system block and backed up in the CPU. When modules are replaced, the new module is therefore immediately ready for use.
With the S7-400 point-to-point link modules, adaptation to the physical transmission media is achieved by plugging in the relevant interface submodules, without the need for external converters.