Functional description
powerSTEP01
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 commands47
can be used in combination with external switch input (see Section 7.14) 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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STMICROELECTRONICS [ ST ]
