Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 1/2
A5E00709327-01
12-1
12 SFCs for Handling Interrupts and
Asynchronous Errors
12.1 Delaying and Disabling Interrupt and Asynchronous
Errors
Purpose of SFC 39 to SFC 42
With these SFCs, you can achieve the following:
Disable interrupts and asynchronous errors with SFC 39 "DIS_IRT" for all
subsequent CPU cycles.
Delay higher priority classes with SFC 41 "DIS_AIRT" until the end of the OB.
Enable interrupts and asynchronous errors with SFC 40 "EN_IRT" or SFC 42
"EN_AIRT."
You program the handling of interrupts and asynchronous errors in the user
program. You must also program the corresponding OBs.
Advantage of SFC 41 and SFC 42
Delaying higher priority interrupts and asynchronous errors by disabling them with
SFC 41 "DIS_AIRT" and then enabling them again with SFC 42 "EN_AIRT" has the
following advantages:
The number of interrupts delayed is counted by the CPU. If you have delayed
interrupts and asynchronous errors, the delay cannot be canceled by standard FC
calls if the interrupts and asynchronous errors are also disabled and then enabled
again in the standard FCs themselves.