Siemens Simatic S7-1500 Function Manual page 77

Glossary
Redundant systems
Redundant systems are identified by the fact that important automation components are
available in multiple units (redundant). If one redundant component fails, control of the
process is maintained.
Retentivity
A memory area whose content is retained even after a power failure and after a transition
from STOP to RUN is retentive. The non-retentive bit memory area, timers and counters are
reset after a power failure and after a STOP-RUN transition.
System states
The system states of the S7-1500R/H redundant system result from the operating states of
the primary and backup CPU. The term system state is used as a simplified expression that
identifies the operating states of the two CPUs that occur at the same time. The S7-1500R/H
redundant system features the STOP, STARTUP, RUN-Solo, SYNCUP and RUN-
Redundant system states.
TIA Portal
Totally Integrated Automation Portal
The TIA Portal is the key to the full performance capability of Totally Integrated Automation.
The software optimizes all operating, machine and process sequences.
Timers
Timers are components of the CPU system memory. The operating system automatically
updates the content of the "timer cells" asynchronously to the user program. STEP 7
instructions define the precise function of the timer cell (e.g. on-delay) and trigger its
execution.
User program
In SIMATIC, a distinction is made between user programs and the firmware of the CPU.
The user program contains all instructions, declarations and data by which a system or
process can be controlled. The user program is assigned to a programmable module (for
example, CPU, FM) and can be structured in smaller units.
Firmware: see glossary entry "Firmware of the CPU"
76
Cycle and response times
Function Manual, 10/2018, A5E03461504-AD