Siemens SIMATIC S7-1500 System Manual page 171

Special features in Startup m ode
● 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.
● 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.
● If a corresponding 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: Time-out (for global error handling only)
The CPU cannot start all other OBs until after the transition to RUN mode.
Response when expected and actual configurations do not m atch
The configuration downloaded to the CPU represents the expected configuration. The actual
configuration is the actual configuration of the automation system. If the expected
configuration and actual configuration deviate from one another, the CPU's behavior is
specified by the setting of the hardware compatibility. For additional information about the
hardware compatibility, see the section Operating mode transitions (Page 174).
Canceling a s tartup
If errors occur during startup, the CPU cancels the startup and returns to STOP mode.
The CPU does not perform startup or interrupts startup under the following conditions:
● You have not inserted a SIMATIC memory card or an invalid one is inserted.
● You have not downloaded a hardware configuration to the CPU.
Parameter assignment of s tartup behavior
You can assign parameters for the behavior of the CPU in the Startup group of the CPU
properties.
Automation system
System Manual, 09/2016, A5E03461182-AD
You can find a description of how to use global and local error handling in the STEP 7
online help.
Commissioning
10.5 Operating modes of the CPU
171