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Interrupt Processing
Response to an alarm request
A reponse to an alarm request must take place in OB2:
•
Read the alarm register byte (x + 3) and transfer it to the process image of the inputs.
Reading the alarm register causes bits 0 to 3 on the module to be deleted. This acknowledges
the alarm and enables the module for further alarms.
•
Bits 0 to 3 of the read alarm register show which of the 4 alarm inputs has initiated an alarm.
All the bits for which the relevant alarm input has been enabled must be evaluated and the
desired alarm response must be made.
•
If bit 0 of the alarm register is set (alarm at input (x + 2).4), bits 4 to 7 of the alarm register
show the status of inputs x.0 to x.3 at the time of initiation of the alarm.
Alarm enable
You must program the alarm enable in restart OBs OB21 and OB22. This is done by setting each bit
under the output addresses (x + 2).0 to (x + 2).3 (see Figure 9.3).
9-12
S5-115U Manual
EWA 4NEB 811 6130-02b
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