Siemens SIMATIC ET 200SP System Manual page 208

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 of inputs during STARTUP, you can access inputs via
direct I/O access.
To initialize outputs during STARTUP, values can be written via the process image or via
direct I/O access. The values are output to the outputs during the transition to 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
● 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 mode. (Figure
"Setting the startup behavior").
● If a corresponding event occurs, the CPU can start the following OBs during startup:
– OB 82: Diagnostics interrupt
– OB 83: Pull/plug interrupt for modules
– OB 86: Rack error
– OB 121: Programming error (only for global error handling)
– OB 122: I/O access error (only for global error handling)
The CPU does not start all other OBs until the transition to RUN mode.
Response when expected and actual configurations do not match
The configuration downloaded to the CPU represents the expected configuration. The actual
configuration is the actual configuration of the ET 200SP distributed I/O system. If the
expected configuration and actual configuration do not match, the setting of the "Comparison
preset to actual configuration" parameter determines the behavior of the CPU. You can find
additional information on hardware compatibility in the section Operating mode transitions
(Page 210).
Distributed I/O system
System Manual, 09/2019, A5E03576849-AJ
You can find a description of how to use global and local error handling in the STEP 7
online help.
Commissioning
11.6 Operating modes of the CPU
207