Plc Program Structure; Plc Operating System - Siemens SINUMERIK 880 SW 6 Planning Manual

1 General Overview
1.2.1 Tasks of the PLC program
Typical tasks of the PLC user program:
• Implementation of monitoring devices
• Machine-specific reactions to malfunctions
• Actuation of auxiliary axes
• Management of a tool magazine
• Management of communication with a host computer
• Gear shifts at request of NC
• Coordination of machine and NC functions by means of disables and enables
• Menu selection for operation configured for specific manufacturers
1.2.2

PLC program structure

The PLC program comprises the PLC operating system and the PLC user program. The PLC
user program is compiled by the machine manufacturer.
By way of support, we offer program packages (function blocks) for recurring complex
functions.

1.2.2.1 PLC operating system

The three principal tasks of the PLC operating system are:
• Organization of system start
• Calling of the PLC user program
• Signal and data transfer via the system's internal interfaces
These main tasks of the PLC operating system are described in greater detail below.
System start-up
The PLC operating system can be adapted to the user-specific channel, spindle and axis
structure of the control by means of the PLC machine data (see "Installation Guide,
Instructions"). When the system starts up, the PLC operating system analyzes the machine
data and configures itself accordingly.
Examples:
• When the system is started a distinction is made between cold restart, warm restart and
start-up mode.
• The number of interfaces to the NC that have to be processed is determined.
• A check is made to establish which OBs have to be called.
• It is determined which inputs and outputs have to be processed, where they are depicted
in the process image and whether the relevant I/O modules are ready.
In the event of contradictory or defective machine data, the PLC operating system branches to
stop status.
OB 20 of the PLC user program is called (if available) from the system start-up routine. This
gives the user the opportunity to insert his own functions in the system start-up.
The system start-up is concluded with the first call of OB 1. Once OB 1 has been fully
processed, the PLC operates cyclically. Refer to the description of the initial setting signals for
further information on system start-up.
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SINUMERIK 880 (PJ)