Siemens simatic hmi op7, Equipment Manual

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7-4
Equipment Manual OP7, OP17
Release 04/99
If there is a condition present in the current process for a message to be
issued – for example, a tag has been reached – a bit is set by the PLC ap-
plication program in the data area for event and alarm messages. The OP
reads the data area after a configured polling time. In this way, a message is
detected as having ”arrived”. The bit is reset by the PLC when the condition
for issuing the message no longer exists. The message is then regarded as
having ”departed”.
7.1.2 Alarm messages
Due to their critical nature, alarm messages have to be acknowledged. This
can be done manually by the operator or automatically by the PLC.
To acknowledge an alarm message manually, press this system key.
ACK
The OP displays unacknowledged alarm messages in flashing mode.
The LED assigned to the Acknowledge key (icon
) also flashes.
After all the alarm messages have been acknowledged, the ACK LED display
changes from flashing to permanently on. Not until all the acknowledged
alarm messages have departed is the LED turned off. In this way, it is impos-
sible for you to forget an alarm message.
If several alarm messages are waiting to be displayed, after one has been
acknowledged the next one is shown, which similarly has to be
acknowledged.
If no more alarm messages are waiting to be displayed, the OP reverts to the
operating level from which it branched to the message level to display the
alarm messages.
During configuration, you can combine several alarm messages to form an
”acknowledgement group”. In this way you can acknowledge all the other
alarm messages (consequential faults) in that acknowledgment group by ac-
knowledging the first alarm message – for example, the cause of the fault –
without all of them having to be output to the display on the OP (group ac-
knowledgement). You can configure up to four acknowledgment groups.
If alarm messages are not assigned to an acknowledgment group, only the
one that happens to be on the display is acknowledged if more are waiting.
There is the possibility of inhibiting the display of frequently occurring alarm
messages for the time being until the OP starts up as a result of a cold or
warm start. Before you can inhibit the display of an alarm message, you must
have logged onto the OP with a password having a password level of at
least 8.
Message bit
procedure
Acknowledging an
alarm message
Acknowledgement
groups, group
acknowledgement
Inhibiting the
display of alarm
messages