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Manual MSX
11.1.3
Input
Maximum step frequency: 500 kHz
Minimum pulse width: one µs
A negative control pulses of 1 µs causes a motor step. The step is done with the falling
flank of the control pulses and the current is changed from run to stop current. If the time
between two control pulses is more than 40 ms, the stop current is activated.
The control pulses sequence must not suddenly start or stop, if the control pulses
)
frequency is higher than the start/stop frequency*
of the motor. Mispositioning of the drive
would be the result.
)
*
The start/stop frequency is defined as that frequency, from which a stepper motor can
start from standstill without losing a step. Typical values for the start/stop frequency are
200 to 2000 Hz. The exact value depends on the load torque and the load inertia of the
motor shaft.
If the motor is to be operated above the start/stop frequency range, the indexer has to
generate frequency ramps to accelerate and decelerate the motor.
11.1.4 Motor Direction Input
If the input optocoupler is not energised, the motor rotates in the preferential direction. If
the input optocoupler is powered, the selected motor direction is reversed.
The signal must only be modified when the motor is at a standstill or turns with the
frequency within the start/stop frequency.
Changing the motor direction when the motor is running will cause step losses and/or stop
the motor.
Important: The signal must be constantly active one μs after the falling flank of the control
pulses (see fig.13).
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Control pulses of the MSX
The preferential motor direction is set via ServiceBus.
MA 2128-A004 EN
46
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