Commissioning
10.6 Operating modes of the CPU
Distributed I/O system
System Manual, 12/2016, A5E03576849-AG
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10.6
Operating modes of the CPU
Introduction
Operating modes describe the status of the CPU. The following operating modes are
possible using the mode selector:
●
STARTUP
●
RUN
●
STOP
In these operating modes, the CPU can communicate, for example, via the PROFINET
interface.
The status LEDs on the front of the CPU indicate the current operating mode.
10.6.1
STARTUP mode
Function
Before the CPU starts to execute the cyclic user program, a startup program is executed.
By suitably programming startup OBs, you can specify initialization tags for your cyclic
program in the startup program. You have the option of programming no, one or several
startup OBs.
Special features during startup
Note the following points regarding the STARTUP mode:
●
All outputs are disabled or react according to the parameter settings for the particular I/O
module: They provide a substitute value as set in the parameters or retain the last value
output and bring the controlled process to a safe operational status.
●
The process image is initialized.
The process image is not updated.
In order to read the current state from inputs during STARTUP, you can access inputs
directly via I/O access.
In order to initialize outputs during STARTUP, values can be written via the process
image or via direct I/O access. The values are output at the outputs during the transition
to the RUN mode.
●
The CPU always starts up in warm restart mode.
–
The non-retentive bit memory, timers and counters are initialized.
–
The non-retentive tags in data blocks are initialized.
●
During startup, cycle time monitoring is not yet running
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