Technical data

SFCs for Handling Interrupts and Asynchronous Errors
System Software for S7-300/400 System and Standard Functions - Volume 1/2
12-8 A5E00709327-01
12.5 Enabling the Processing of Higher Priority Interrupts
and Asynchronous Errors with SFC 42 "EN_AIRT"
Description
With SFC 42 "EN_AIRT" (enable alarm interrupts), you enable the processing of
higher priority interrupts and asynchronous errors that you previously disabled with
SFC 41 "DIS_AIRT." Each SFC 41 call must be canceled by an SFC 42 call.
Example
If, for example, you have disabled interrupts five times with five SFC 41 calls, you
must cancel these calls with five SFC 42 calls.
Parameter Declaration Data Type Memory Area Description
RET_VAL OUTPUT INT I, Q, M, D, L Number of delays still programmed on
completion of SFC 42 or error message.
Return Value and Error Information
Refer to Evaluating Errors with Output Parameter RET_VAL
How you evaluate the error information of the RET_VAL parameter is explained in
Chapter "Evaluating Errors with Output Parameter RET_VAL". This chapter also
contains the general error information for the SFCs. The following table contains all
the error information specific to SFC 42 that can be output with the RET_VAL
parameter.
Return Value and Error
Information
Description
N "n" shows the number of SFC 41 calls not yet canceled by SFC 42 calls
(interrupt processing is only enabled again when "n" = 0).
W#16#8080 The function has been called again although interrupt processing was
already enabled.