Operating Modes Of The Cpu; Startup Mode - Siemens SIMATIC S7-1500 System Manual

Commissioning

10.5 Operating modes of the CPU

10.5 Operating modes of the CPU
Introduction
Operating modes describe the states of the CPU. The following operating states are possible
via the mode selector:
● STARTUP
● RUN
● STOP
In these operating modes, the CPU can communicate, for example, via the PROFINET IO
interface (X1).
The status LEDs on the front side of the CPU indicate the current operating mode.
10.5.1

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. That is, you can set up one or several startup OBs in your
program, or none at all.
Special features in Startup mode
● All outputs are disabled or react according to the parameter settings for the respective
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 operating mode.
● The process image is initialized.
● The process image is not updated.
In order to read the current state of inputs during STARTUP, you can access inputs by
direct I/O access.
In order to initialize outputs during STARTUP, you can write the values 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 a warm restart.
– The non-retentive bit memories, timers and counters are initialized.
– The non-retentive tags in data blocks are initialized.
● During startup, no cycle time monitoring is running yet.
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System Manual, 12/2014, A5E03461182-AC