opto engineering ITALA - Encodervalue Wrapping Management

Itala | INSTRUCTION MANUAL
• 4-phase mode: encoder counter is updated (incremented or decremented) for every full
cycle (i.e. for every sequence 00 - 10 - 11 - 01)
0
0
1
1
2
2
3 4
5
6 7
20
21
22
23
24
25
26
27
28
29
9 10 11
12
138
14
15
16
17
18
19
Encoder A
Encoder B
High resolution
4- phase
3
4 5
6
Figure 68: Encoder modes: High resolution (above) vs 4-phase (below).
6.10.4 EncoderValue wrapping management
EncoderValue is a positive value, ranging from 0 to 65535.
When encoder output mode is set to position mode, reverse motion is considered in Encoder-
Value computation: since this value cannot be negative, backward movements cause the encoder
to reverse count, from 65535 to 0, as depicted in Fig.69.
In this scenario, if reverse motion is not correctly managed, spurious pulses could arise.
Consider the following exemple, where EncoderDivider is set equal to 20000.
Consider also a number of backward steps that lead EncoderValue to be equal 15000, i.e. a value
smaller than EncoderDivider. When forward motion restarts, a spurious encoder pulse arises
when EncoderValue equals EncoderDivider (i.e. 20000).
In order to avoid unwanted encoder pulses, the following condition must be satisfied:
Maximum backward steps < (2
16
− 1) − EncoderDivider (13)
In case Eq.12 could not be guaranteed, spurious encoder pulses must be managed by user appli-
cation.
v1.12 - eng 91