Siemens SIMATIC S7-400 Configuration And Use Manual page 15

Racks
The various modules of the S7-400 automation system are inserted and fastened
in a rack. The backplane bus of the rack is divided into two different bus systems:
• I/O bus: The P bus is a parallel backplane bus, which is designed for fast
exchange of input and output signals.
• C bus: The C bus is a serial backplane bus, which is designed for the exchange
of larges amounts of data.
A total of 22 racks can be connected with one another via interface modules.
Power Supply
The power supply module provides the required operating voltage via the
backplane bus of the rack. The available supply voltage and required drive power
of the modules determines the selection of the correct power supply. Power
supplies are also available with diagnostics and can be configured redundantly if
required.
Signal Modules
A wide variety of digital and analog input and output modules (signal modules, SM)
are available for adapting to a wide-range of actuators and sensor signals. Signal
modules are also available with alarm processing and diagnostics.
Function Modules
Function modules (FM) are specialists for integrating the following plant functions:
Counting and measuring
•
• Positioning
• Controlling
• Cam controlling
Interface Modules
Interface modules (IM) are needed to interconnect racks in multi-tier
configurations.
Communication Modules
Communication tasks can be realized directly via the interfaces of the CPU or
using special communication modules (communication processors, CP) to connect
to the following networks or couplers:
• PROFIBUS DP
• PROFINET
• Industrial Ethernet (including IT functionality)
• Point-to-point connections
Automation System S7-400 Configuration and Use
A5E00442711-02
SIMATIC S7 - an Overview
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