Siemens SIMATIC HMI Operating Instructions Manual page 109

Not pressed
Pressed
● Bit coding of illuminated pushbutton LEDs
Off
On permanently
● Bit coding of handwheel
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
The numbers in the following table represent a byte in the PLC.
The difference in pulses at times t
thus the direction of rotation.
Establish the following values:
Mobile Panel 277F IWLAN
Operating Instructions, 12/2007, A5E01003940-01
State
LED status
– 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.
Evaluation time
Pulses, forwards
t
1
t
2
t
3
t
4
T1
0
1
T1
0
1
Handwheel
Pulses, backwards
255 (≙ -1) 245 (≙ -11)
10 245 (≙ -11)
10
15
and t allows you to determine the resulting value and
n n+1
Operator controls and displays
5.5 Operator controls
Evaluation
--
Pulses, forwards: 11
Pulses, backwards: 0
Resulting value: +11
4 Pulses, forwards: 0
Pulses, backwards: 15
Resulting value: -15
5 Pulses, forwards: 5
Pulses, backwards: 1
Resulting value: +4
T2
0
1
T2
0
1
to t .
1 4
109