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5 Functionality
A/B Trigger Debounce
A debouncing logic can be enabled by setting ABTriggerDeBounce=True. It is implemented with a
watermark value of the EncoderCounter (see Fig. 5.24). Suppose ABTriggerDirection=fwd, then
the watermark value is increased with the increments of the EncoderCounter. If
EncoderCounter decreases, e.g. Due to bouncing problems, the watermark value is hold
unchanged. Triggers are then only generated when the watermark value increases.
Figure 5.24: A/B Trigger Debouncing, example with ABMode=quad
The A/B Trigger Debounce mode can also be used for another issue:
In some applications the conveyor belt may stop between parts. In practice the conveyor belt
stops and retraces by a small amount which may cause a misalignment in the system. If
ABTriggerDirection=fwd is used and the Debounce mode is enabled and the conveyor belt starts
again in forward direction, no triggers are generated for the amount that the conveyor belt
retraced (see Fig. 5.25). The highest value of the EncoderCounter is stored as the watermark.
Triggers are only generated when the EncoderCounter is at the watermark level.
3 u a d A / B M o d e , D e b o u n c i n g
)
B
0
1
G r a y C o u n t e r
0
1
E n c o d e r C o u n t e r
W a t e r m a r k
0
1
T r i g g e r F w d
Figure 5.25: A/B Trigger Debouncing, example with ABMode=quad; example for encoder retracing
.
62
A
B
G r a y C o u n t e r
0
1
E n c o d e r C o u n t e r
0
1
W a t e r m a r k
0
1
T r i g g e r F w d
2
3
0
1
2
3
0
2
3
4
5
6
7
8
2
3
4
5
6
7
8
f o r w a r d m o v e m e n t
h i g h w a t e r m a r k i s s a v e d
* o u n c i n g
2
3
2
3
0
3
0
2
3
2
3
4
3
4
2
3
4
1
0
3
2
1
0
1
9
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5
4
5
9
b a c k w a r d m o v e m e n t
1
5
5
2
3
0
1
2
3
0
6
7
8
9
1 0
1 1
1 2
1 0
1 1
1 2
f o r w a r d m o v e m e n t
t r i g g e r w h e n w a t e r m a r k i s e x c e e d e d
1
2
1 3
1 4
1 3
1 4
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