AN1495 datasheet(22/25 Pages) STMICROELECTRONICS

22 / 25 page

Code

AN1495

22/25

Doc ID 8700 Rev 3

ld a, (microtable2, x)

ld y, torquescaler

mul y, a

ld TBOC1LR, y

jp pwmend

; end of routine for forward step

doclockrev:

;direction is reverse

dec stepstate

jrne rev002

bres PBDR, #5

; activate reset to maintain sync

rev002:

ld a, stepstate

and a, #%00011111

ld x,a

inc a

; 7 or 8 =>> 8 or 9

and a, #%00001110

cp a, #8

; 8 or 9

jrne rev001

bset PBDR,#4

; rising edge for clock

rev001:

ld a,(microtable1,x)

ld y,torquescaler

mul y,a

ld TAOC1LR, y

ld a, (microtable2,x)

ld y, torquescaler

mul y, a

ld TBOC1LR, y

jp pwmend

; The lookup table holds the magnitude of a sine wave normalized to a peak

value of 256.

; Each line of 16 entries represents 90 degrees or one full step (thus 16

microsteps per

step).

; Table reference labels at 45 degrees (microtable1) and 135 degrees

(microtable2) are

provided for convenience

; to allow easy lookup of two waveforms with 90 degree phase relationship.

; Since only five bits (0 to 31) of the stepstate table index are used,

references using

microtable1 roll over through

; just the first two lines of the table while references using microtable2

stay within

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