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Process-Dependent Operator Guidance
11.4 System Keyboard Assignment
Application
Create a data area for your system keyboard on the PLC. When you press a
key, the corresponding bit is set in the keyboard assignment. The bit is set for
as long as the corresponding key is pressed. Releasing the key resets the bit.
By an evaluation of this area, the operator's attention can be drawn, for
example, by means of an event message to incorrect operation of a key.
Configuring
If the data area for system keyboard bits is to be used, it must be specified
system keyboard
during configuration as the area pointer and created on the PLC. The system
assignment
keyboard assignment is a data area having a fixed length of two data words.
Figure 11-6 shows its configuration for an OP3.
Keyboard group bit
Figure 11-6 Keyboard Assignment for the OP3
The keyboard assignment is transferred spontaneously to the PLC whenever a
modification is registered on the OP3. There is therefore no need to configure
a polling time.
The keyboard group bit is used as a check bit. It is set to 1 every time the
keyboard assignment is transferred from the OP3 to the PLC and should be
reset after the data area has been evaluated by the application program.
Regular reading of the group bit makes it possible to ascertain in the user's
program whether the system keyboard assignment has been transferred again.
11-6
7
6
5 4
3
2
1
0
.
SHIFT
+/–
9
8
7
6
5 4
3
2
1
0
7
0
6
5
4
3
2
1
Bit number
1st data word
2nd data word
Operator Panel OP3
Edition 11/99
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