The SFC 17 and the SFC 18 should always be called from a FB after you
have assigned the respective system attributes to this FB.
When generating messages with the SFC 17 and SFC 18, the operating system uses one
system resource for the duration of the signal cycle.
For SFC 18 , the signal cycle lasts from the SFC call SIG = "1" until another call with SIG
= "0". For SFC 17, this time period also includes the time until the incoming signal is
acknowledged by one of the reported display devices, if necessary.
If, during the signal cycle, the message-generating block is overloaded or deleted, the
associated system resource remains occupied until the next restart.
Messages sent by means of the SFC 17 can be acknowledged via a display device. The
acknowledgement status for the last "message entering state" and the signal status of the
last SFC 17-call may be determined by means of the SFC 19 ALARM_SC.
Messages that are sent by SFC 18 are always acknowledged implicitly. The signal status
of the last SFC 18-call may be determined by means of the SFC 19 ALARM_SC.
The SFCs 17 and 18 occupy temporary memory that is also used to save the last two
signal statuses with a time stamp and the associated value. When the call to the SFC
occurs at a time when the signal statuses of the two most recent "valid" SFC-calls has not
been sent (signal overflow), then the current signal status as well as the last signal status
are discarded and an overflow-code is entered into temporary memory. The signal that
occurred before the last signal will be sent as soon as possible including the overflow-
code.
The maximum number of SFC 17- and SFC 18-calls depends on the type of CPU being
used. A resource bottleneck (instance overflow) can occur when the number of SFC-calls
exceeds the maximum number of dynamic instances.
This condition is indicated by means of an error condition in RET_VAL and via the regis-
tered display device.
Parameters
Parameter Declaration Data type Memory block Description
SIG INPUT BOOL I, Q, M, D, L The signal that triggered the message.
ID INPUT WORD I, Q, M, D, L Data channel for messages: EEEEh
EV_ID INPUT DWORD Const.
(I, Q, M, D, L)
Message number
(0: not permitted)
SD INPUT ANY I, Q, M, D, T, C Associated value
RET_VAL OUTPUT INT I, Q, M, D, L Error information
Associated value
Maximum length: 12byte
Valid data types
System resources
Message acknowledge-
ment
Temporarily saving
Instance overflow
SD
VIPA SPEED7
Integrated Standard
System Functions > SFC 17 - ALARM_SQ and SFC 18 - ALARM_S
HB00 | OPL_SP7 | Operation list | en | 18-30 662
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