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64tass Source follows.

explanation of the algorithm: https://www.eit.lth.se/fileadmin/eit/courses/eitf35/2017/CORDIC_For_Dummies.pdf

this routine was used in this prod: https://www.pouet.net/prod.php?which=91340 (a more size optimised version ofcourse)

loopcount = $0f

x = $10

y = $12

xxl = $14 xxh = $15

yyl = $16 yyh = $17

xxshiftl = $18 xxshifth = $19

yyshiftl = $1a yyshifth = $1b

anglelo = $1c anglehi = $1d

sanglelo = $1e sanglehi = $1f

• = $1000

sei

lda #20
sta 53272
lda #200
sta xxl
lda #100
sta yyl
lda #0
sta xxh
sta yyh
jsr cordic
inc $d020
;jmp *-3

lda #0
sta x
sta y

-

lda x
sec
sbc #20
sta xxh
lda #0
sbc #$01
sta xxl

lda y
sec
sbc #12
sta yyh
lda #0
sbc #$80
sta yyl

lda y
asl
tay
lda mul40+0,y
clc
adc x
sta dst+1
lda mul40+1,y
adc #0
sta dst+2

jsr cordic

dst sta $0400

inc x
lda x
cmp #40
bne -

lda #0
sta x

inc y
lda y
cmp #25
bne -


jmp *

neg

lda xxh
bpl +
lda xxshiftl
eor #$ff
clc
adc #$01
sta xxshiftl
lda xxshifth
eor #$ff
adc #$00
sta xxshifth

+

lda yyh
bpl +
lda yyshiftl
eor #$ff
clc
adc #$01
sta yyshiftl
lda yyshifth
eor #$ff
adc #$00
sta yyshifth

+ rts

cordic lda #0

sta loopcount
sta sanglelo
sta sanglehi

lda xxh
bpl notneg

lda xxl
eor #$ff
clc
adc #$01
sta xxl
lda xxh
eor #$ff
adc #$00
sta xxh

lda yyl
eor #$ff
clc
adc #$01
sta yyl
lda yyh
eor #$ff
adc #$00
sta yyh

lda #$80
sta sanglehi

notneg cordicloop

lda xxl
sta xxshiftl
lda xxh
sta xxshifth

lda yyl
sta yyshiftl
lda yyh
sta yyshifth

ldx loopcount	
beq noshift

jsr neg	;if xxshifth (xxh) neg make pos

-

lda xxshifth
cmp #$80
ror xxshifth
ror xxshiftl

lda yyshifth
cmp #$80
ror yyshifth
ror yyshiftl
dex
bne -

jsr neg	;iff xxshifth was neg make neg again

noshift

lda yyh
bmi yisneg

yispos

;Xnew = X + (Y >> LoopNum) 
lda xxl
clc
adc yyshiftl
sta xxl

lda xxh
adc yyshifth
sta xxh

; Ynew = Y - (X >> LoopNum) 
lda yyl
sec
sbc xxshiftl
sta yyl

lda yyh
sbc xxshifth
sta yyh

ldx loopcount
lda sanglelo
clc
adc angleslo,x
sta sanglelo

lda sanglehi
adc angleshi,x
sta sanglehi

jmp cordicloopend

yisneg

; Xnew = X - (Y >> LoopNum) 
lda xxl
sec
sbc yyshiftl
sta xxl

lda xxh
sbc yyshifth
sta xxh

; Ynew = Y + (X >> LoopNum) 

lda yyl
clc
adc xxshiftl
sta yyl

lda yyh
adc xxshifth
sta yyh

ldx loopcount
lda sanglelo
sec
sbc angleslo,x
sta sanglelo
lda sanglehi
sbc angleshi,x
sta sanglehi

cordicloopend

inc loopcount
lda loopcount
cmp #8
bne cordicloop

lda sanglehi
rts

;360 = 2 * pi
;360 = 255
;(2*pi)/65536 = step

angleslo .for ue=0,ue<8,ue=ue+1

;.warn tan(atan(1.0/(2**ue)))

.byte <round(atan(1.0/(2**ue))/((2*pi)/65536))
;.warn ue
.next	

angleshi .for ue=0,ue<8,ue=ue+1

;.warn tan(atan(1.0/(2**ue)))

.byte >round(atan(1.0/(2**ue))/((2*pi)/65536))
;.warn ue
.next	

mul40 .for ue=0,ue<25,ue=ue+1

.word $0400+ue*40
.next