EVAL6208N Datasheet, PDF (15/27 Pages) STMicroelectronics – DMOS DRIVER FOR BIPOLAR STEPPER MOTOR

L6208
time. The drive mode is selected by the HALF/FULL input and the current state of the sequence generator as
described below. A rising edge of the CLOCK input advances the state machine to the next state. The direction
of rotation is set by the CW/CCW input. The RESET input resets the state machine to state.
HALF STEP MODE
A HIGH logic level on the HALF/FULL input selects Half Step Mode. Figure 16 shows the motor current wave-
forms and the state diagram for the Phase Sequencer Generator. At Start-Up or after a RESET the Phase Se-
quencer is at state 1. After each clock pulse the state changes following the sequence 1,2,3,4,5,6,7,8,… if CW/
CCW is high (Clockwise movement) or 1,8,7,6,5,4,3,2,… if CW/CCW is low (Counterclockwise movement).
NORMAL DRIVE MODE (Full-step two-phase-on)
A LOW level on the HALF/FULL input selects the Full Step mode. When the low level is applied when the state
machine is at an ODD numbered state the Normal Drive Mode is selected. Figure Fig. 17 shows the motor cur-
rent waveform state diagram for the state machine of the Phase Sequencer Generator. The Normal Drive Mode
can easily be selected by holding the HALF/FULL input low and applying a RESET. AT start -up or after a RE-
SET the State Machine is in state1. While the HALF/FULL input is kept low, state changes following the se-
quence 1,3,5,7,… if CW/CCW is high (Clockwise movement) or 1,7,5,3,… if CW/CCW is low (Counterclockwise
movement).
WAVE DRIVE MODE (Full-step one-phase-on)
A LOW level on the pin HALF/FULL input selects the Full Step mode. When the low level is applied when the
state machine is at an EVEN numbered state the Wave Drive Mode is selected. Figure 18 shows the motor cur-
rent waveform and the state diagram for the state machine of the Phase Sequence Generator. To enter the
Wave Drive Mode the state machine must be in an EVEN numbered state. The most direct method to select the
Wave Drive Mode is to first apply a RESET, then while keeping the HALF/FULL input high apply one pulse to
the clock input then take the HALF/FULL input low. This sequence first forces the state machine to sate 1. The
clock pulse, with the HALF/FULL input high advances the state machine from state 1 to either state 2 or 8 de-
pending on the CW/CCW input. Starting from this point, after each clock pulse (rising edge) will advance the
state machine following the sequence 2,4,6,8,… if CW/CCW is high (Clockwise movement) or 8,6,4,2,… if CW/
CCW is low (Counterclockwise movement).
Figure 16. Half Step Mode
3
4
5
2
6
1
8
7
I_OUTA
I_OUTB
Start Up or Reset
CLOCK
12345678
D01IN1320
Figure 17. Normal Drive Mode
I_OUTA
3
4
5
2
6
I_OUTB
1
8
7
Start Up or Reset
CLOCK
13 5 7 1 3 5 7
D01IN1322
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