1.2 What Hardware is Required?
The central hardware components required are two S7-300 or S7-400 stations or one of each. On
each station is a CPU and a connection for a DP master system.
The two stations are linked by means of a bus system via which they can exchange information.
Connection to the peripheral devices is made via two DP master systems - one on station A and on
one station B.
ET 200M distributed I/O devices with redundant-backup DP slave interfaces (e.g. IM 153-3) are
connected to the two DP master systems. The DP slave interface makes it possible to switch from the
first to the second interface in the event of a fault, thereby enabling process status data to be passed
to the peripherals by the second DP master.