User Manual

AND8399/D
http://onsemi.com
6
SLA Check
Although the microcontroller controls the stepper motor
driver, it’s always possible that an offset is created
unwontedly. By reading out the Microstep Position (Status
Register 3) the microcontroller can check if an offset is
created or not.
Table 1 displays all possible Microstep Positions for all
stepping modes except full step. If at any moment the read
out Microstep Position is equal to a value given in this table
(for a certain stepping mode), no offset is created (see also
Figure 9). If another value is read out, an offset is created and
no microstep position will be located on the ”coil current
zero crossing” (see also Figure 10). The SLA−voltage will
not represent the real Bemf of the stepper motor.
0
16
32
4
8
12
20
24
28
36
40
44
48
52
56
60
64
68
72
76
80
84
88
92
96
100
104
108
112
116
120
124
Figure 9. Possible Microstepping Positions for
Correct Bemf Measurement (1/8 Microstepping)
I
X
I
Y
2
18
34
6
10
14
22
16
30
38
42
46
50
54
58
62
66
70
74
78
82
86
90
94
98
102
106
110
114
118
122
126
Figure 10. Example of 1/8 Microstepping with Offset
I
X
I
Y