Siemens SIMATIC S7-400 Hardware And Installation Manual page 285

Programmable Programmable controllers are electronic control devices whose
Logic Controller functions are stored in the controller in the form of a program. The
(PLC) 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.
Programming A personal computer with a special compact design, suitable for
Device (PG) industrial conditions. A Siemens programming device is completely
equipped for programming the SIMATIC programmable logic
controllers.
Protective Ground 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
RAM The RAM (Random Access Memory) is a semiconductor memory with
random access (read/write memory).
Reference Ground
Reference The potential on which the voltages of the various circuits are based
Potential and according to which they are measured.
Retentive Data Retentive data are not lost after a power failure, if a backup battery is
provided.
Revision Level 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.
Run-Time Error Errors that occur in the programmable controller (that is, not in the
process) during execution of the user program.
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
www.gkbpx.com
Ground
Glossary
Glossary-11