A4980LP View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
'A4980LP' PDF : 44 Pages View PDF
A4980
Automotive, Programmable Stepper Driver
arithmetic operators to be used, within the microcontroller, to
determine the size of the next step increment. Table 6 shows the
binary equivalent of each decimal number between –16 and +16.
Each increase in the Step Angle Number represents a forwards
movement of one-sixteenth microstep. Each decrease in the Step
Angle Number represents a reverse movement of one-sixteenth
microstep.
To move the motor one full step, the Step Angle Number must be
increased or decreased by 16. To move the motor one half step,
the Step Angle Number must be increased or decreased by 8. For
quarter step the increase or decrease is 4 and for eighth step, 2.
So, for example, to continuously move the motor forwards in
quarter-step increments, the number 4 (000100) is repeatedly
written to SC[5..0] through the serial interface Run register (see
figure 10). To move the motor backwards in quarter step incre-
ments, the number -4 (111100) is repeatedly written to SC[5..0]
(see figure 11). The remaining bits in the Run register should be
set for the required configuration and sent with the step change
number each time.
The step rate is controlled by the timing of the serial interface.
It is the inverse of the step time, tSTEP, shown in figure 10. The
motor step only takes place when the STRn goes from low to
Table 6. Binary Equivalents
2’s
Decimal Complement
Decimal
0
000000
1
000001
–1
2
000010
–2
3
000011
–3
4
000100
–4
5
000101
–5
6
000110
–6
7
000111
–7
8
001000
–8
9
001001
–9
10
001010
–10
11
001011
–11
12
001100
–12
13
001101
–13
14
001110
–14
15
001111
–15
16
010000
–16
+4
1010101010000100
2’s
Complement
111111
111110
111101
111100
111011
111010
111001
111000
110111
110110
110101
110100
110011
110010
110001
110000
SDI
SCK
STRn
tSTEP
Figure 10. Serial interface sequence for quarter step in forward direction
-4
1010101010111100
SDI
SCK
STRn
Figure 11. Serial interface sequence for quarter step in reverse direction
Allegro MicroSystems, Inc.
25
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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