Siemens SINUMERIK 804D sl Commissioning Manual page 276

Fundamentals
15.5 PLC program
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
Overview Creating a PLC program (Page 54)
276
parameters are output to all modules in single-processor mode
CNC Part 1 (NCK, PLC, drive)
Commissioning Manual, 11/2006, 6FC5397-2AP10-2BA0