Glossary - Siemens SIMATIC S7-400 Reference Manual

Glossary

2-conductor/3-conductor/4-conductor connection
Method of connecting to the module, for example, connecting resistance thermometers or
resistors to the front connector of the analog module or loads to the voltage output of an analog
output module.
2-wire transducer/4-wire transducer
Type of transducer (2-wire transducer: Power supply via terminals of the
analog input module; 4-wire transducer: power supply via separate connectors of the
transducer)
Address
An address identifies a specific operand or range of operands, examples: input I 12.1; memory
word MW25; data block DB3.
Automation system
An automation system is a → programmable controller comprising a → central rack, a CPU and
various input/output modules.
Backplane bus
The backplane bus is a serial data bus over which modules communicate with each other and
over which they are supplied with the necessary voltage. The connection between modules is
established by bus connectors.
Backup battery
The backup battery ensures that the → user program on the → CPU is not lost in the event of
a power failure and that defined data areas, bit memory, timers, and counters are also retained.
Backup voltage, external
The same backup can be achieved as with a backup battery if a backup voltage (direct voltage
between 5 V and 15 V) is applied to the "EXT.-BATT." socket of the CPU.
The external backup voltage is required to replace a power supply module if the user program
and data stored in a RAM (for example, bit memory, timers, counters, system data, integrated
clock) needs to be backed up while the module is exchanged.
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
441