Siemens Simatic S7-400 - Manual (Page 607)

Glossary-1
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Glossary
Address
An address denotes a specific operand or address area; examples of this are:
input I 12.1; memory word MW 25; data block DB 3.
Aggregate current
Sum of the currents of all output channels on a digital output module.
Backplane bus
The backplane bus is a serial data bus that is used by the modules to
communicate with each other and to supply them with the voltage they require.
The interconnection of the modules is established by the bus connector.
Backup battery
The backup battery ensures that the
³
user program is stored in a
powerfail-proof manner in the
³
CPU, and that defined data areas and memory
markers, timers and counters are kept ³ retentively.
Backup voltage, external
You can obtain the same kind of backup if you apply backup voltage to the ”EXT.-
BATT.” socket of the CPU (DC voltage between 5 V and 15 V) as you can with a
backup battery.
External backup voltage is required if you want to replace a power supply module
and to provide a backup supply while the user program and data (for example,
memory markers, timers, counters, system data, integrated clock) stored in RAM
are to be buffered for the time it takes to replace the module.
Bus
A bus is a transmission medium that interconnects several nodes. Data
transmission can be serial or parallel, and be performed over electric conductors
or fiber-optic cables.