Technical data

Table Of Contents
Generating Block-Related Messages
System Software for S7-300/400 System and Standard Functions - Volume 2/2
24-10
A5E00739858-01
24.4 Generating Block-Related Messages with
Acknowledgment with SFB 33 "ALARM"
Description
SFB 33 "ALARM" monitors a signal.
Default mode (that is, acknowledgement triggered reporting is disabled): The block
generates a message both on a positive edge (event entering state) and on a
negative edge (event leaving state). You can have up to ten associated values sent
with the message.
Acknowledgement triggered reporting is enabled: After an incoming message is
generated for the signal, the block will no longer generate messages until you have
acknowledged this incoming message on a displaying device.
(see also the introduction on Generating Block-Related Messages with SFBs.
The message is sent to all stations logged on for this purpose.
When the SFB is first called, a message with the current signal state is sent.
The ACK_UP output is reset at the rising edge. It is set when your
acknowledgment of the event entering the state has arrived from a logged on
display device.
The situation for the ACK_DN output is analogous: this is reset at the negative
edge. It is set when your acknowledgment of the event leaving the state is received
from a logged on display device. Once your acknowledgment has been received
from a logged on display device, the acknowledgment information is passed on to
all other stations logged on for this purpose.
One message memory with 2 memory blocks is available for each instance of
SFB33 "ALARM". For information on saving signal transitions to intermediate
memory refer to the section "Signal transition detection" in the Introduction to
Generating Block-Related Messages with SFBs.
SFB 33 "ALARM" complies with the IEC 1131-5 standard.
Parameter Declaration Data Type Memory Area Description
EN_R INPUT BOOL I, Q, M, D, L,
constant
Control parameter enabled to receive
that decides whether the outputs
ACK_UP and ACK_DN are updated at
the first block call (EN_R=1) or not
(EN_R=0). If EN_R=0 the output
parameters ACK_UP and ACK_DN
remain unchanged.
SIG INPUT BOOL I, Q, M, D, L The signal to be monitored
ID INPUT WORD I, Q, M, D, L,
constant
Data channel for messages:
W#16#EEEE ID is only evaluated at
the first call.