Advanced Parallel I/O - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 349

C4

Current f low

1st

N S

S N S N

C2 C1

C3

2nd

Figure 7.37c ■ Stepper motor full step 3

S

C4

N

1st S

N

C2 C1

S

Current flow

C3

2nd

N

Figure 7.37d ■ Stepper motor full step 4

We can also rotate the stepper motor in the counterclockwise direction. This can be done
by reversing the polarities of coils C3 and C4 in Figure 7.37b and d. Figure 7.38 shows the coun-
terclockwise sequence.
The stepper motor may also be operated with half steps. A half step occurs when the rotor
(in a four-pole step) is moved to eight discrete positions (45 degrees). To operate the stepper motor
in half steps, sometimes both coils may have to be on at the same time. When two coils in close