Siemens SIMATIC S7-400H System Manual page 42

Installation of a CPU 41x–H
5.1 Control and display elements of the CPUs
Slot for interface modules
You can insert an H-Sync module in this slot.
MPI/DP interface
You can, for example, connect the following devices to the MPI interface of the CPU:
● Programming devices
● Operator control and monitoring devices
● Further S7-400 or S7-300 controllers, see section Multipoint interface (MPI) (Page 57)
Use the bus connection connector with the oblique cable outlet, see the
System, Hardware and Installation
The MPI interface can also be configured for operation as DP master and therefor as a
PROFIBUS DP interface with up to 32 DP slaves.
PROFIBUS DP interface
The PROFIBUS DP interface supports the connection of distributed I/O, PGs and OPs.
Setting the rack number
Use the selector switch on the rear panel of the CPU to set the rack number. The switch has
two positions: 1 (up) and 0 (down). One CPU is allocated rack number 0, and the partner
CPU is assigned rack number 1. The default setting of all CPUs is rack number 0.
Connecting an external backup voltage to the "EXT. BATT." socket
The S7-400H power supply modules support the use of two backup batteries. This allows
you to:
● Back up the user program stored in RAM.
● Retain bit memory, timers, counters, system data and data in dynamic data blocks.
● Back up the internal clock.
You can achieve the same backup by connecting a DC voltage between 5 V DC and 15 V DC
to the "EXT. BATT." socket of the CPU.
Properties of the "EXT. BATT." input:
● Polarity reversal protection
● Short-circuit current limiting to 20 mA
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manual.
S7–400 Automation
System Manual, 09/2007, A5E00267695-03
S7-400H