AN857 查看數據表（PDF） - Microchip Technology

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AN857

Brushless DC Motor Control Made Easy

Microchip Technology 

FIGURE 4:

#define

#define

#define

#define

COMMUTATION CODE SEGMENT

DrivePort

SensorMask

SensorPort

DirectionBit

PORTC

B’00000111’

PORTE

PORTA, 1

Commutate

movlw

andwf

xorwf

btfsc

return

SensorMask

SensorPort

LastSensor, w

STATUS, Z

;retain only the sensor bits

;get sensor data

;test if motion sensed

;zero if no change

;no change - return

xorwf

btfss

goto

LastSensor, f

DirectionBit

FwdCom

;replace last sensor data with current

;test direction bit

;bit is zero - do forward commutation

movlw

movwf

movlw

goto

FwdCom

movlw

movwf

movlw

Com2

addwf

btfsc

incf

HIGH RevTable

PCLATH

LOW RevTable

Com2

HIGH FwdTable

PCLATH

LOW FwdTable

LastSensor, w

STATUS, C

PCLATH, f

;reverse commutation

;get MS byte to table

;prepare for computed GOTO

;get LS byte of table

;forward commutation

;get MS byte of table

;prepare for computed GOTO

;get LS byte of table

;add sensor offset

;page change in table?

;yes - adjust MS byte

call GetDrive

movwf DriveWord

return

;get drive word from table

;save as current drive word

GetDrive

movwf PCL

FwdTable

retlw B’00000000’

retlw B’00010010’

retlw B’00001001’

retlw B’00011000’

retlw B’00100100’

retlw B’00000110’

retlw B’00100001’

retlw B’00000000’

RevTable

retlw B’00000000’

retlw B’00100001’

retlw B’00000110’

retlw B’00100100’

retlw B’00011000’

retlw B’00001001’

retlw B’00010010’

retlw B’00000000’

;invalid

;phase 6

;phase 4

;phase 5

;phase 2

;phase 1

;phase 3

;invalid

;invalid

;phase /6

;phase /4

;phase /5

;phase /2

;phase /1

;phase /3

;invalid

AN857

 2002-2011 Microchip Technology Inc.

DS00857B-page 5

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