Start­up And Synchronization Of Nck Plc; Cyclical Mode (Ob 1) - Siemens SINUMERIK 828D Function Manual

13.8.1 Start­up and synchronization of NCK PLC
Loading the basic program
The basic program must be loaded with the S7 tool when the PLC is in the Stop state. This ensures that all
blocks in the basic program will be initiated correctly the next time they are called. Otherwise, undefined states
can occur in the PLC (e.g. blinking of all PLC LEDs).
Start­up,
The synchronization of NCK and PLC is performed during startup. The system and user data blocks are checked
for integrity and the most important basic program parameters are verified for plausibility. In cases of errors, the
basic program produces an alarm (visible on HMI) and switches the PLC to the Stop state.
A warm restart is not provided, i.e. following system initialization, the operating system runs organization block
OB 100 and always commences cyclic execution at the start of OB 1.
Synchronization
The PLC is synchronized with the HMI and NCK and CP during power­up.
Sign-of-life
After a correct initial start and the first complete OB1 cycle (initial setting cycle) the PLC and NCK continuously
exchange sign of life signals. If the sign of life from the NCK fails to materialize, the PLC/NCK interface is
initialized and the signal "NCK CPU ready" in DB 10 is set to FALSE.
13.8.2

Cyclical mode (OB 1)

General
The NCK PLC interface is processed completely in cyclic mode. From a chronological viewpoint, the basic
program runs ahead of the user program. In order to minimize the execution time of the basic program, only the
control/status signals are transmitted cyclically; transfer of the auxiliary functions and G functions only takes
place on request.
The following functions are performed in the cyclic part of the basic program:
• Transmission of the control/status signals
• Distribution of the auxiliary functions
• M decoding (M00 - M99),
• M, S, F distribution
• Transmission of the MCP signals via the NCK (on the SINUMERIK 840D only)
• Acquisition and conditioning of the user errors and operating messages.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
P3: Basic PLC Program for SINUMERIK 840D sl
13.8 Structure and functions of the basic program
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