PXD20RM Datasheet, PDF (1439/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Chapter 42
Stepper Stall Detect (SSD)
42.1 Introduction
42.1.1 Overview
The SSD block connects to one stepper motor (SM) with two coils. It can be used to monitor the movement
of the SM to detect that the attached gauge pointer has reached the stall position of the scale.
Basis of the movement detection is to drive one of the coils and to integrate the back EMF (electromotive
force) induced in the other coil. This back EMF is present only if the SM is rotating. Therefore, if the
integral of the back EMF exceeds a certain threshold, the SM is still rotating; otherwise it can be regarded
as being stalled.
The SSD block shares the pins connected to the SM coils together with the motor controller block
responsible for driving the SM in the main application (e.g. moving the gauge pointer to a certain position
of the scale).
PXD20 Microcontroller Reference Manual, Rev. 1
42-1