Glossary · Motion control and drives
Step/direction interface
Also known as: Step/Dir, Pulse/direction interface, Step and direction interface
German: Step/Dir-Schnittstelle
In motion control, a step/direction interface is a command interface of a motor driver with two digital inputs: each pulse on the step input moves the motor by one step or microstep, and the level on the direction input sets the direction of rotation.
- Motion control
In one sentence
A step/direction interface commands a driver with two signals: each step pulse moves one (micro)step, the direction level sets the rotation.
Example
A PLC's high-speed pulse output sends step and direction signals to the drivers of a small XY gluing table.
How it applies
- Engineering: The controller generates the motion profile as a pulse train; the driver only executes steps. Speed equals pulse frequency, so the maximum pulse rate of the output limits speed at high microstep settings. Many drivers add an enable input.
- Commissioning: Signal levels, minimum pulse width, setup time of the direction signal before the next step and the active edge must match both sides. Shielded cables prevent noise pulses from being counted as steps.
- Operation: The interface has no feedback: the controller doesn't learn about Step loss unless an encoder or stall output is wired back.
- Documentation: Give a timing diagram and a table with levels, pulse width, maximum frequency and the direction convention (which level means clockwise, seen from which side of the shaft).
Step/direction interface vs. serial interface
With step/direction, the controller sends each step. With a serial interface such as Serial Peripheral Interface (SPI) or Universal asynchronous receiver-transmitter (UART), it sends parameters and target positions, and a Motion control IC generates the steps itself. Many ICs offer both: step/direction for motion, a serial interface for configuration.