Benefit

• The power of the S7-400 is scalable thanks to a graded range of CPUs; the capacity for I/O is almost unlimited.
• The power reserves of the CPUs enable new functions to be integrated without further hardware investment, e.g. processing of quality data, user-friendly diagnosis, integration into higher-level MES solutions or high-speed communication via bus systems.
• The S7-400 can be structured in a modular way; there is a widely varied range of modules available both for centralized configurations and distributed structures. This results in very cost-effective spare parts handling.
• The configuration of the distributed I/O of the S7-400 can be modified during operation (Configuration in Run). In addition signal modules can be removed and inserted while live (hot swapping). This makes it very easy to expand the system or replace modules in the event of a fault.
• The storage of the complete project data including symbols and comments on the CPU simplifies service and maintenance calls.
• Safety engineering and standard automation can be integrated into a single S7-400 controller; plant availability can be increased through the redundant structure of the S7-400.
• Many of the S7-400 components are also available in a SIPLUS version for external environmental conditions, e.g. extended temperature range (-25?+60°C) and for use where there is aggressive atmosphere/condensation.
• The high-speed backplane bus of S7-400 ensures efficient linking of central I/O modules

Design

An S7-400 system basically comprises a rack, power supply, and central processing unit. It can be installed and expanded in a modular way. All modules can be positioned freely next to the power supply plugged in on the left. The S7-400 has a rugged design without a fan. Signal modules can be hotswapped.A multi-faceted module range can be used for central expansions as well as for simple configuration of distributed topologies with ET 200.
In a centralized expansion, additional mounting racks are connecteddirect to the central controller.

In addition to the standard mounting racks, aluminum mounting racks with 9 and 18 slots are also available. These aluminum racks are highly resistant to unfavorable environmental conditions, and they are more rigid and around 25% lighter.

Multicomputing

Multicomputing, that is, the simultaneous operation of several CPUs in one S7-400 central controller, offers users different benefits:

• The overall performance of an S7-400 can be shared by means of multicomputing. For example, complex tasks in technologies such as open-loop control, computing or communication can be split and assigned to different CPUs. Each CPU is assigned its own, local I/O for this purpose.
• Some tasks can also be disconnected from each other in multicomputing, that is, one CPU processes the time-critical process tasks and another handles the non-time-critical tasks.

In multicomputing operation, all CPUs behave like a single CPU, that is, when one CPU goes to STOP, the others are also halted. The actions of several CPUs can be coordinated selectively by instruction via synchronization calls.In addition, data exchange between the CPUs takes place at an extremely high speed via the “global data” mechanism.

Data/program memory

The size of the work memory is determined CPU that can be selected from a finely graded range of CPUs.The integral load memory (RAM) is sufficient for small to mediumsized programs. For larger programs, the load memory is enlarged by plugging in RAM or FEPROM memory cards (64 KB to 64 MB).

Special functions

The S7-400 CPUs have some highly useful special functions:

• Simpler and faster upgrade due to firmware update via network from an engineering workstation
• Additional write-protection (for e.g. no component download from PC to CPU) via a system function
• Optional know-how protection by reading the serial number of the memory card, so that it is ensured that the program runs only with the particular memory card

An integrated data record gateway permits integrated accessto data records across different bus systems and networkboundaries e.g. a control-level PC can communicate via PROFINETwith a lower-level S7-400 controller and the field devicesconnected to it via PROFIBUS.