PLC concepts
4.1 Execution of the user program
S7-1200 Programmable controller
94 System Manual, 03/2014, A5E02486680-AG
For detailed information on events that trigger an update interrupt, refer to the manufacturer's
documentation for the DPV1 or PNIO slave.
Table 4- 11 Start information for update OB
Profile OBs execute if a DPV1 or PNIO slave triggers a profile-specific interrupt.
For detailed information on events that trigger a profile interrupt, refer to the manufacturer's
documentation for the DPV1 or PNIO slave.
Table 4- 12 Start information for profile OB
Event execution priorities and queuing
The CPU processing is controlled by events. An event triggers an interrupt OB to be
executed. You can specify the interrupt OB for an event during the creation of the block,
during the device configuration, or with an ATTACH or DETACH instruction. Some events
happen on a regular basis like the program cycle or cyclic events. Other events happen only
a single time, like the startup event and time delay events. Some events happen when the
hardware triggers an event, such as an edge event on an input point or a high speed counter
event. Events like the diagnostic error and time error event only happen when an error
occurs. The event priorities and queues are used to determine the processing order for the
event interrupt OBs.
The CPU processes events in order of priority where 1 is the lowest priority and 26 is the
highest priority. Prior to V4.0 of the S7-1200 CPU, each type of OB belonged to a fixed
priority class (1 to 26). With V4.0, you can assign a priority class to each OB that you
configure. You configure the priority number in the attributes of the OB properties.
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