Operator controls and displays
5.5 Operator controls
Mobile Panel 277F IWLAN
Operating Instructions, 12/2007, A5E01003940-01
109
State
T1
T2
Not pressed
0
0
Pressed
1
1
● Bit coding of illuminated pushbutton LEDs
LED status
T1
T2
Off
0
0
On permanently
1
1
● Bit coding of handwheel
– A setpoint is not specified for the handwheel.
– After start-up of the HMI device, the bytes "n+4" to "n+5" are set to zero.
Rotation of the handwheel produces positive or negative pulses depending on the
rotation direction. The number of positive pulses are stored in bits I0 to I7. The number
of negative pulses are stored in bits D0 to D7. The values are entered in binary format,
where bit 0 is the lowest and bit 7 is the highest valued bit.
A complete handwheel revolution yields 50 pulses.
– Every pulse of the handwheel is added to byte "n+4" or "n+5" depending on the
direction of rotation. There are no negative values. When the possible value range is
exceeded, there is an overflow:
If a value of 255 is increased by one pulse, a value of 0 results.
Example of bit coding for handwheel
The following table includes an example for rotation direction determination. The pulses are
stored in bytes "n+4" and "n+5" and are measured during the points in time t
1
to t
4
.
The numbers in the following table represent a byte in the PLC.
Handwheel
Evaluation time
Pulses, forwards
Pulses, backwards
Evaluation
t
1
255 (≙ -1)
245 (≙ -11)
--
t
2
10
245 (≙ -11)
Pulses, forwards: 11
Pulses, backwards: 0
Resulting value: +11
t
3
10
4
Pulses, forwards: 0
Pulses, backwards: 15
Resulting value: -15
t
4
15
5
Pulses, forwards: 5
Pulses, backwards: 1
Resulting value: +4
The difference in pulses at times t
n
and t
n+1
allows you to determine the resulting value and
thus the direction of rotation.
Establish the following values:
