; main loop
;
;	r28,r29,r30 is the phase accumulator
;  	r24,r25,r26 is the adder value determining frequency
;
; 	add value to accumulator
;	load byte from current table in RAM
;	output byte to port
;	repeat 
		; clear accumulator 

	    	clr     r28
		clr 	r29				
		clr	r30	
          
		add	r28,r24			
LOOP1: 		adc	r29,r25		; 1
		adc	r30,r26		; 1
        	ldi     r31,1           ; 1 even step by default
        	sbrc    r29,7           ; 1 Skip if bit 7 in r29 cleared
        	ldi     r31,2           ; 1 odd step instead
      		ld      r0,z		; 2
		out	PORTD,r0	; 1
		add	r28,r24		; 1
		adc	r29,r25		; 1
		adc	r30,r26		; 1
        	ldi     r31,1           ; 1 even step
        	sbrc    r29,7           ; 1 Skip if bit 7 in r29 cleared
        	ldi     r31,2           ; 1 odd step
		ld      r0,z		; 2
		add	r28,r24		; 1 timeing
		out	PORTD,r0	; 1
		rjmp	LOOP1		; 2 => 20 / 2 = 10 cycles


;******************************************************************************
; data tables
;******************************************************************************

	; force table to begin at 256 byte boundary

	.org 0x100

sine2x256x8:	
	
; 512 step sinewave table
; to be copied to SRAM starting at 0x100

; even
.db 128,131,134,137,140,143,146,149,152,156,159,162,165,168,171,174
.db 176,179,182,185,188,191,193,196,199,201,204,206,209,211,213,216
.db 218,220,222,224,226,228,230,232,234,236,237,239,240,242,243,245
.db 246,247,248,249,250,251,252,252,253,254,254,255,255,255,255,255
.db 255,255,255,255,255,255,254,254,253,252,252,251,250,249,248,247
.db 246,245,243,242,240,239,237,236,234,232,230,228,226,224,222,220
.db 218,216,213,211,209,206,204,201,199,196,193,191,188,185,182,179
.db 176,174,171,168,165,162,159,156,152,149,146,143,140,137,134,131
.db 128,124,121,118,115,112,109,106,103,99,96,93,90,87,84,81
.db 79,76,73,70,67,64,62,59,56,54,51,49,46,44,42,39
.db 37,35,33,31,29,27,25,23,21,19,18,16,15,13,12,10
.db 9,8,7,6,5,4,3,3,2,1,1,0,0,0,0,0
.db 0,0,0,0,0,0,1,1,2,3,3,4,5,6,7,8
.db 9,10,12,13,15,16,18,19,21,23,25,27,29,31,33,35
.db 37,39,42,44,46,49,51,54,56,59,62,64,67,70,73,76
.db 79,81,84,87,90,93,96,99,103,106,109,112,115,118,121,124
; odd
.db 129,132,135,138,141,144,147,150,154,157,160,163,166,169,172,175
.db 178,180,183,186,189,192,194,197,200,202,205,207,210,212,214,217
.db 219,221,223,225,227,229,231,233,235,236,238,239,241,242,244,245
.db 246,247,248,249,250,251,252,253,253,254,254,255,255,255,255,255
.db 255,255,255,255,255,254,254,253,253,252,251,251,250,249,248,247
.db 245,244,243,241,240,238,237,235,233,232,230,228,226,224,222,219
.db 217,215,213,210,208,205,203,200,198,195,192,190,187,184,181,178
.db 175,173,170,167,164,161,158,154,151,148,145,142,139,136,133,130
.db 126,123,120,117,114,111,108,105,101,98,95,92,89,86,83,80
.db 77,75,72,69,66,63,61,58,55,53,50,48,45,43,41,38
.db 36,34,32,30,28,26,24,22,20,19,17,16,14,13,11,10
.db 9,8,7,6,5,4,3,2,2,1,1,0,0,0,0,0
.db 0,0,0,0,0,1,1,2,2,3,4,4,5,6,7,8
.db 10,11,12,14,15,17,18,20,22,23,25,27,29,31,33,36
.db 38,40,42,45,47,50,52,55,57,60,63,65,68,71,74,77
.db 80,82,85,88,91,94,97,101,104,107,110,113,116,119,122,125

UpDateMode:

	cpi Mode,0
	brne LoopMode
		Off:
		clr r0
		st Z+,r0
		cpi r31,1
		brne Off
		cpi r31,255
		brne Off

	rjmp ModeDone

LoopMode:
	cpi Mode,2
	brne ABC
		ldi ZH, high(sine2x256x8 *2)              ; Initialize Z pointer
		ldi ZL, low(sine2x256x8 *2)
		ldi YH,1
		clr YL
sine512:
		lpm r0,z+
		st y+,r0
		cpi YH,3
		brne sine512
		cpi YL,255
		brne sine512


ABC:

ModeDone:

ret