Siemens S7-400 Reference Ground, Reference Potential, Retentive Data, Release version

Glossary

R

RAM

The RAM (Random Access Memory) is a semiconductor memory with random access (read/write memory). May be used as for storing 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 which 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 can 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.

Glossary-12

Automation System S7-400 Hardware and Installation A5E00850741-01