Siemens S7-400 installation manual Varistor, Warm Restart, Watchdog interrupt, Work Memory

Glossary

V

Varistor

Voltage-dependent resistor

W

Warm Restart

During a CPU startup and before cyclic program processing starts (OB1), either OB101 (hot restart), or OB100 (restart / warm start), or OB102 is processed first. Prerequisite for the execution of the “hot restart” function is a backup of all CPU data.

The data of all data areas ( timers, counters, flags, DBs) are retained. The process-image input table is read in and the STEP 7 user program processed starting at the last breakpoint STOP, power failure).

Watchdog interrupt

Generated cyclically within a configurable time pattern by the S7-400 CPU. Triggers the execution of a corresponding OB. Starting point of the clock cycle is the operational transition from STOP to RUN.

Work Memory

The work memory is the RAM (Random Access Memory) in the CPU to which the STEP 7 user program is automatically reloaded from the load memory. The processor executes the program in the work memory in RUN mode.

Glossary-16

Automation System S7-400 Hardware and Installation A5E00850741-01