Start-Up
SINUMERIK 802C base line
4-9
Start-Up
4.3 Starting up the PLC
General
The PLC is a store-programmable logic controller for simple machines. It has
no hardware of its own and is used as a software PLC in the SINUMERIK 802C
base line control system.
The task of the PLC is to control machine-related functional sequences.
The PLC executes the user program cyclically. A PLC cycle is always executed
in the same sequence of order.
z
Update process image (inputs, outputs, user interface, timers)
z
Process communication requests (Operator Panel, PLC 802 Programming
Tool)
z
Execute user program
z
Evaluate alarms
z
Output process image (outputs, user interface)
The PLC executes the user program cyclically, starting from the first up to the
final operation. Access from user program is only carried out via the process
image and not directly to the hardware inputs or outputs. The hardware inputs
and outputs are updated by the PLC at the beginning and at the end of
program execution. The signals are thus stable over a PLC cycle.
The user program can be created by means of the PLC 802 Programming Tool
using the programming language S7-200 in conjunction with ladder diagrams
(LAD). A ladder diagram is a graphical programming language to represent
electrical circuit diagrams.
This Documentation describes the program structure and the instruction set of
the PLC in detail.
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