Siemens S7-400 Installation Manual page 301

ISA Bus
The ISA bus is the standard bus in the AT-compatible PC. It is looped through the
M7-400 module assembly via the 120-pin expansion sockets and plugs of the
individual M7-400 modules.
Isolated
In the case of isolated I/O modules, the reference potentials of the control and load
circuits are galvanically isolated from each other, for example, by optocouplers,
relay contacts, or transformers. The I/O circuits can be connected to a common
potential.
K
Keyswitch
The keyswitch is the mode selector switch of the CPU. The keyswitch is operated
with a key which can be withdrawn.
L
Load Memory
The load memory is part of the S7-400 CPU. It contains objects created by the
programming device. It can be either a plug-in memory card or an integrated
memory.
Load Power Supply
Power supply for the signal and function modules and the process I/O connected to
them.
Local Data
³ Data, Temporary
Logic Block
In SIMATIC S7, a logic block is a block that contains part of the STEP 7 user
program. The other type of block is a data block which contains only data.
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Glossary
Glossary-9