Glossary
Glossary-11
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
Programmable controllers are electronic control devices whose
functions are stored in the controller in the form of a program. The
structure and wiring of a PLC therefore do not depend on the actual
functions of the controller. Programmable controllers and computers
have similar structure: they consist of a CPU (central processing unit)
with memory, input/output modules, and an internal bus system. The
I/O and programming language are tailored to the requirements of
open-loop control technnology.
A personal computer with a special compact design, suitable for
industrial conditions. A Siemens programming device is completely
equipped for programming the SIMATIC programmable logic
controllers.
Connection via protective conductor to a common ground conductor for
the exposed, conductive parts of electrical apparatus which are not
normally live, but at which a voltage may be present in the event of a
fault, and which are jointly protected via a protective device.
R
The RAM (Random Access Memory) is a semiconductor memory with
random access (read/write memory).
³ Ground
The potential on which the voltages of the various circuits are based
and according to which they are measured.
Retentive data are not lost after a power failure, if a backup battery is
provided.
Products with the same order number are differentiated by their
revision level. The revision level is increased for upwardly-compatible
function expansions, for changes due to production reasons (use of
new components) and for fault correction.
Errors that occur in the programmable controller (that is, not in the
process) during execution of the user program.
Programmable
Logic Controller
(PLC)
Programming
Device (PG)
Protective Ground
RAM
Reference Ground
Reference
Potential
Retentive Data
Revision Level
Run-Time Error
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