Reference guide

Cluster (Dashboard) Using S12HZ256 as a Single-Chip Solution Designer Reference Manual, Rev. 0
Freescale Semiconductor 7
Chapter 1
Introduction
1.1 Introduction
This manual describes the design of a cluster board (dashboard) using Freescale’s S12HZ256
microcontroller unit (MCU). This is a single-chip design for the whole system.
The traditional cluster board uses a cross coil motor to drive the analog pointers (actuator) which move
either clockwise or counterclockwise to indicate the car speed, engine rotation speed, fuel level, engine
temperature, etc. This technology is well established and widely used throughout the world. However,
when the cross coil motor is being assembled, it requires an alignment process. The cross coil motor
displacement linearity is also a drawback in regards to the displacement accuracy (linearity), as it may
need motor fine tuning during cluster board manufacturing. In view of this, stepper motors can be one
alterative solution in this application. In addition, the Moving Magnet Technology (MMT) is more mature
for stepper motors nowadays.
The following are some advantages in having the magnet of a stepper motor move relative to a stationary
coil set.
1. The stationary drive coils are beneficial to a motor structure, as they can deal effectively with heat
dissipation.
2. There are no “flying” leads since the coils are stationary which leads to improved longevity of the
motor.
3. The weight of the stationary coils does not affect the maximum velocity of the motor.
4. There is no frictional wear out because the moving magnet concept does not make contact with
any of the stationary elements of motor.
For cluster applications in the automotive segment, Freescale offers the S12H family of devices which
can support up to six stepper motors. These devices also include, as a single-chip solution, a 32 x 4
segment LCD driver to show time and mileage updates on a LCD panel. The designers have also
integrated Stepper Stall Detection (SSD) in the new derivative of the S12HZ family. This derivative
supports up to four stepper motors with SSD.
This manual is based on the 9S12HZ256 features for designing a cluster application.
NOTE
This document is written for the user who is familiar with the S12H256
family and CodeWarrior for S12 and cluster applications. All hardware
schematic diagrams and firmware source codes are available as reference
materials.