Startup Operating State - Siemens SIMATIC S7-1500 System Manual

11.4.2

STARTUP operating state

Response
Before the CPU starts to execute the cyclic user program, a startup routine is executed.
By programming startup OBs, you can specify initialization tags for your cyclic program in the
startup routine. You can program one or more startup OBs, or none at all.
Points to note
● All outputs are disabled or react according to the parameter settings for the relevant
module: They provide a configured substitute value or retain the last value output and
switch the controlled process to a safe operating state.
● The process image is initialized.
● The process image is not updated.
To read the current state of inputs during STARTUP, you can access inputs with direct
I/O access.
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 RUN.
● 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.
● Cycle time monitoring is not yet running during startup.
● The CPU processes the startup OBs in the order of the startup OB numbers. The CPU
processes all programmed startup OBs regardless of the selected startup type (see
"Setting the startup behavior" figure below).
● If a relevant event occurs, the CPU can start the following OBs in startup:
– OB 82: Diagnostics interrupt
– OB 83: Removal/insertion of modules
– OB 86: Rack error
– OB 121: Programming error (only for global error handling)
– OB 122: I/O access error (for global error handling only)
The CPU cannot start any other OBs until after the transition to RUN.
SIMATIC Drive Controller
System Manual, 11/2019, A5E46600094-AA
You can find a description of how to use global and local error handling in the STEP 7
online help.
Commissioning
11.4 Operating states of the CPU
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