AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 42

• Manufacturer Part Number: AN1914
• Description: 3-Phase BLDC Motor Control with Sensorless Back EMF Zero Crossing Detection Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

SW Design
7.3.4.2 Commutation Control - Starting state
7.3.4.3 Commutation Control - Set Running
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detected during last
commutation period
No Zero Crossing
and commutation registers are preset. If Zero Crossing already happen during Per_Toff time period,
the commutation period is corrected using Corrective Calculation 2. When the commutation time
expires, then a new commutation is performed.
This state is almost wholly serviced by the BLDC Zero Crossing algorithms which are documented in
Motor Control.pdf, chapter BLDC Motor Commutation with Zero Crossing Sensing (see
Section
requests and commutation control registers. Other BLDC Zero Crossing algorithms are called,
according to the request flags. The state services are located in main loop and in Cmt (commutation)
Timer Interrupt.
The starting state is the Running state as described in
This state services the transition from Starting (Back-EMF Acquisition) state to Running state by the
BLDC Zero Crossing algorithms (see
Calculate Next Commutation
after No Zero Crossing
Corrective Calculation 1.
12.1). First the bldczcHndlr is called with actual time from Cmt Timer Counter to control
Zero Crossing Missed
during Per_Toff
DSP56F80x MC PWM Module in Motor Control Applications
Running - Begin
Freescale Semiconductor, Inc.
Preset Next Commutation
For More Information On This Product,
settings and timing
Figure 7-8. Substates - Running
Go to: www.freescale.com
Section
commutation period
Detected/Missed during last
Zero Crossing
Calculate Next Commutation
after Zero Crossing Missed
Corrective Calculation 2.
12.1) according to the following actions:
Zero Crossing Get
Figure
motor Commutation
Calculate Next Commutation
after Zero Crossing Get
7-8.
commutation time
(T_Next) expired