Siemens SIMATIC ET 200AL System Manual page 327

5.2.3 Triggering a hardware interrupt
During a hardware interrupt, the CPU interrupts the processing of the user program and
processes the hardware interrupt OB (e.g., OB 40). The event that triggered the interrupt is
entered in the start information of the hardware interrupt OB.
Note
Diagnostics "Hardware interrupt lost" (from I/O module)
Avoid creating hardware interrupts cyclically.
If the hardware interrupt load is too high, hardware interrupts can get lost depending on the
number of I/O modules and the communication load.
5.2.4 Triggering an insert/remove module interrupt
When an insert/remove module interrupt occurs, the CPU interrupts execution of the user
program and processes the insert/remove module interrupt OB (OB 83). The event that
triggered the interrupt is entered in the start information of the insert/remove OB.
The pull/plug OB (OB 83) is also triggered for all subsequent I/O modules, because the ET-
Connection and/or the power supply is interrupted.
IM 157-1 PN (6ES7157-1AB00-0AB0)
Equipment Manual, 05/2021, A5E32347036-AE
Interrupts, error messages, diagnostics and system alarms
5.2 Interrupts
31