Glossary
Glossary-12
Automation System S7-400 Hardware and Installation
A5E00850741-01
R
RAM
The RAM (Random Access Memory) is a semiconductor memory with r andom
access (read/write memory). May be used as for s toring interim data for later use.
This memory is not retentive, that is, its data are lost after power failure.
Reference Ground
→ Ground
Reference Potential
The potential on w hich the voltages of the various circuits are based and according
to which they are measured.
Retentive Data
Retentive data are not lost after a power failure, if a backup battery is provided.
Release version
Used to distinguish products with the same order number. Incremented with each
up-compatible functional enhancement, manufacturing-specific change (use of new
parts / components) and for bugfixes.
Run-Time Error
Errors that occur in the programmable controller (that is, not in the process) during
execution of the user program.
S
Scan Cycle Time
The scan cycle time is the time the CPU takes to run the user program once
through.
Shared Data
Shared data c an be accessed by any code block ( FC, FB, OB). These include bit
memory M, inputs I, outputs Q, timers T, counters C, and data blocks DB. Global
data can be accessed either absolutely or symbolically.
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