Siemens SINUMERIK 840D sl Commissioning Manual page 308

Fundamentals
15.4 PLC program
Start-up behavior of the PLC
There are both remanent and non-remanent areas for the markers, times and counter. The
areas are continuous and are divided by a parameterizable limit, where the area with the
higher-value address range is defined as the non-remanent area. Data blocks are always
remanent.
Start-up mode COLD RESTART (OB 100)
If the remanent area has no battery backup (backup battery is empty) start-up is prevented.
The following operations are performed during a cold restart:
● UStack, BStack and non-retentive flags, timers and counters are deleted
● The process output image (POI) is deleted
● Process and diagnostics alarms are cancelled
● The system status list is updated
● Parameterization objects of modules (from SD100 onwards) are evaluated or default
● Execute cold restart (OB100)
● Read in process input image (PII)
● Cancel command ouptput inhibit (BASP)
Basic program, start-up part (FB1)
FB 1 (start-up block of the PLC program) must be assigned variables.
Parameter FB 1
A precise description of the variables and options for modifying their parameterization is
given in:
Literature
Function Manual Basic Functions; Basic PLC Program
Cyclical mode (OB 1)
From a chronological viewpoint, the basic program runs ahead of the PLC user program.
The complete processing of the NCKPLC interface is carried out in cyclic mode.
A cyclic monitoring function is activated between PLC and NCK once power-up and the first
OB1 cycle have been completed. A PLC failure produces alarm "2000 Sign-of-life monitoring
PLC".
See also
Creating a PLC program (Page 51)
308
parameters are output to all modules in single-processor mode
Commissioning Manual, 07/2007, 6FC5397-2AP10-3BA0
IBN CNC: NCK, PLC, drive