Table of Contents
Advertisement
Appendix
A.2 Evaluation of the operator control elements
• Bit coding of handwheel
Example of bit coding for handwheel
The following table contains an example showing how to determine the rotation direction
using pulses stored in Bytes n+3 and n+4 that were measured between time t
The numbers in the following table represent a byte in the PLC.
Evaluation
t
1
t
2
t
3
t
4
Based on the difference in pulses at times t
rotation direction can be determined. From the table, take the number of pulses forwards and
pulses backwards
• at the tim t
• at time t
From this, you determine the resulting value. This is calculated as:
Resulting value =
pulses, forwards, t
t
)
n
A-8
– A setpoint is not specified for the handwheel.
– After startup of the HMI device, bytes n+3 to n+4 (see figure) are set to zero.
Rotation of the handwheel produces positive or negative pulses depending on the
rotation direction. The number of positive pulses is stored in bits I0-I7, and the number
of negative pulses is stored in Bits D0-D7.
Values are entered in binary format, whereby Bit 0 is the least significant bit and Bit 7
is the most significant bit.
A complete handwheel revolution yields 50 pulses.
– Each pulse of the handwheel is added to the appropriate byte (n+3 or n+4), depending
on the direction or rotation. There are no negative values. If the possible value range
is exceeded, an overflow occurs.
If a value of 255 is increased by one pulse, a value of 0 results.
time
Pulses, forwards
255 (≙ -1)
10
10
15
and
n
.
n+1
- pulses, backwards, t
n+1
Handwheel
Pulses, backwards
245 (≙= -11)
245 (≙ -11)
4
5
and t
, the resulting value and, thus, the
n
n+1
- (pulses, backwards, t
n
Operating Instructions (Compact), Edition 07/2005
and t
.
1
4
Evaluation
--
Pulses, forwards: 11
Pulses, backwards: 0
Resulting value: +11
Pulses, forwards: 0
Pulses, backwards: 15
Resulting value: -15
Pulses, forwards: 5
Pulses, backwards: 1
Resulting value: +4
- pulses, backwards,
n+1
Mobile Panel 177 (WinCC flexible)
Advertisement
Table of Contents
