Siemens S7-400 Installation Manual page 294

Glossary
BIOS
Basic Input Output System
BIOS is understood to mean the part of the software which creates the link
between hardware and the operating system, for example, MS-DOS. This software
is stored in an EPROM.Basic Input Output System
Examples of important sections are the loader for the operating system, the
(hardware) setup for defining the hardware configuration and for setting the time.
Bit Memory (M)
A memory area in the system memory of a SIMATIC CPU. This area can be
accessed using write or read access (bit, byte, word, and double word). The bit
memory area can be used by the user to store intermediate results. It can be
accessed bit by bit, byte by byte, word by word, or double word by double word.
Building Ground
The connection between data processing equipment and ground, whereby no
unacceptable functional interference to data processing equipment is caused by
external effects, such as interference caused by power systems. The connection
must be in the form of a low-noise ground.
Bus
A bus is a transfer medium which interconnects several nodes. Data transmissions
can be serial or parallel over electical conductors or fiber-optic cables.
C
Chassis Ground
The chassis ground comprises all interconnected inactive parts of an apparatus,
which even in case of a fault cannot take dangerous touch voltages.
Communications Processor
Communications processors are modules for point-to-point and bus connections.
Compress
The PG online function "Compress" is used to shift all valid blocks in the RAM of
the CPU evenly and without any gaps to the beginning of the user memory. All
gaps caused by deleting or correcting blocks are thus removed.
Glossary-2
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04