Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
24-1
24 Generating Block-Related Messages
24.1 Introduction to Generating Block-Related Messages
with SFBs
SFBs for Generating Block-Related Messages
You can generate a block-related message by calling one of the following SFBs in
your program:
SFB 36 "NOTIFY"
SFB 31 "NOTIFY_8P"
SFB 33 "ALARM"
SFB 34 "ALARM_8"
SFB 35 "ALARM_8P"
These SFBs have the following properties:
Save with SFBs 36 "NOTIFY" and 31 "NOTIFY_8P", all detected 0 -> 1 or 1 -> 0
signal transitions when a block is called will result in a message transfer.
When the default reporting procedure is set (acknowledgement triggered
reporting disabled), the SFBs 33 "ALARM", 34 "ALARM_8" and 35
"ALARM_8P" will also generate a message when any signal transitions are
detected when a block is called.
If, on the other hand, you have enabled acknowledgement triggered reporting,
not all signal transitions will trigger a message transfer (see below for details).
Following execution of the block, the associated values (inputs SD_i) are read
completely and assigned to the message (see "Send and Receive Parameters"
in Common Parameters of the SFBs/FBs and SFCs/FCs for S7
Communication.)
In terms of consistency compared with high-priority classes, the following
associated values are consistent:
Every associated value SD_i is inherently consistent.
With the status parameters DONE, ERROR and STATUS, you monitor the
processing status of the block (see "Status Parameters" in Common Parameters of
the SFBs/FBs and SFCs/FCs for S7 Communication.)
Note
The parameters ID and EV_ID are only evaluated at the initial call of the block (the
actual parameters or the defined values of the instance).