Siemens SIMATIC S7 System Manual page 71

The queue overflow occurred condition results if the interrupts are occurring faster than they
can be processed. The number of pending (queued) events is limited using a different queue
for each event type. If an event occurs when the corresponding queue is full, a time error
event is generated.
All time error events trigger the execution of OB 80 if it exists. If an OB 80 is not included in
the user program, then the device configuration of the CPU determines the CPU reaction to
the time error:
● The default configuration for time errors, such as starting a second cyclic interrupt before
● The default configuration for exceeding the maximum time is for the CPU to change to
You can use the RE_TRIGR instruction to reset the maximum cycle time. However, if two
"maximum cycle time exceeded" conditions occur within the same program cycle without
resetting the cycle timer, then the CPU transitions to STOP, regardless of whether OB 80
exists. See the section on "Monitoring the cycle time" (Page 73).
OB 80 includes startup information that helps you determine which event and OB generated
the time error. You can program instructions inside OB 80 to examine these startup values
and to take appropriate action.
Table 4- 3
Input
fault_id
csg_OBnr
csg_prio
No time error interrupt OB 80 is present when you create a new project. If desired, you add a
time error interrupt OB 80 to your project by double-clicking "Add new block" under "Program
blocks" in the tree, then choose "Organization block", and then "Time error interrupt".
Understanding diagnostic error events
Analog (local), PROFINET, and PROFIBUS devices are capable of detecting and reporting
diagnostic errors. The occurrence or removal of any of several different diagnostic error
conditions results in a diagnostic error event. The following diagnostic errors are supported:
● No user power
● High limit exceeded
● Low limit exceeded
● Wire break
● Short circuit
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
the CPU has finished the execution of the first, is for the CPU to stay in RUN.
STOP.
Startup information for OB 80
Data type
BYTE
OB_ANY
UINT
Description
16#01 - maximum cycle time exceeded
16#02 - requested OB cannot be started
16#07 and 16#09 - queue overflow occurred
Number of the OB which was being executed when the error
occurred
Priority of the OB causing the error
97BPLC concepts
4.1 Execution of the user program
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