Motorola M68HC08 manual Main Software Flowchart, Bldc Commutation and Zero Crossing Selection

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Software Design

Main Software Flowchart

3.2.5Back-EMF Sensing Circuit.The zero crossing selection is provided by the multiplexer setting.

As shown in Figure 5-2, the commutation and back-EMF zero crossing selection process is split into two actions:

•Preset commutation and zero crossing selection

•The preset means setting the buffered registers and RAM variables for commutation

•Set commutation and zero crossing selection

•The setting means loading the registers with buffered variables

The implementation is described in Implementation Notes - 5.6.2

BLDC Commutation and Zero Crossing Selection.

5.4 Main Software Flowchart

The main software flowchart incorporates the main routine entered from the reset and interrupt states. The main routine includes initializing the MCU and the main loop. The flowcharts are shown in Figure 5-4, Figure 5-5, and Figure 5-6.

MCU Initialization is entered only after system reset. It provides initialization of system registers, ports, and CPU clock. The MCU Initialization is provided in MCUInit() function.

After MCU Initialization the Application Initialization is executed as AppInit() function, which performs the following actions. First the zero current offset of the dc-bus current measurement path is calibrated. This offset on the ADC input should be 1.65 V at zero current. This is implemented in the hardware design, in order to be able to measure negative and positive current values. The status registers are initialized and PWM generator is started. Also, timer 1 is started at the right moment to be synchronized with the PWM generator. This way the current measurement is executed at the defined moment of the PWM signal.

DRM028 — Rev 0		Designer Reference Manual
MOTOROLA	Software Design	83
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