POWERSTEP01 datasheet(28/92 Pages) STMICROELECTRONICS

28 / 92 page

Functional description

powerSTEP01

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DocID025022 Rev 5

The HardStop command stops the motor instantly, ignoring deceleration constraints and

keeping the rotor position (a holding torque is applied).

The SoftHiZ command causes the motor to decelerate with a programmed deceleration

value until the MIN_SPEED value is reached and then forces the bridges into high

impedance state (no holding torque is present).

The HardHiZ command instantly forces the bridges into high impedance state (no holding

torque is present).

7.7.5

Step-clock mode

In Step-clock mode the motor motion is defined by the step-clock signal applied to the STCK

pin. At each step-clock rising edge, the motor is moved one microstep in the programmed

direction and absolute position is consequently updated.

When the system is in Step-clock mode the SCK_MOD flag in the STATUS register is

raised, the SPEED register is set to zero and motor status is considered stopped regardless

of the STCK signal frequency (the MOT_STATUS parameter in the STATUS register equal

to “00”).

7.7.6

GoUntil and ReleaseSW commands

In most applications the power-up position of the stepper motor is undefined, so an

initialization algorithm driving the motor to a known position is necessary.

The GoUntil and ReleaseSW commands can be used in combination with external switch

input (see Section 7.14 on page 33) to easily initialize the motor position.

The GoUntil command makes the motor run at target constant speed until the SW input is

forced low (falling edge). When this event occurs, one of the following actions can be

performed:



ABS_POS register is set to zero (home position) and the motor decelerates to zero

speed (as a SoftStop command)



ABS_POS register value is stored in the MARK register and the motor decelerates to

zero speed (as a SoftStop command).

If the SW_MODE bit of the CONFIG register is set to ‘0’, the motor does not decelerate but

it immediately stops (as a HardStop command).

The ReleaseSW command makes the motor run at a programmed minimum speed until the

SW input is forced high (rising edge). When this event occurs, one of the following actions

can be performed:



ABS_POS register is set to zero (home position) and the motor immediately stops (as

a HardStop command)



ABS_POS register value is stored in the MARK register and the motor immediately

stops (as a HardStop command).

If the programmed minimum speed is less than 5 step/s, the motor is driven at 5 step/s.

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