hgr: more work on constant-time hplot

fireworks/hgr.s

@@ -80,13 +80,19 @@ bkgnd_loop:
 
 
 
-msktbl:	.byte $81,$82,$84,$88,$90,$A0,$C0
+msktbl:	.byte $81,$82,$84,$88,$90,$A0,$C0	; original
+
 
 hposn:
 	; F411
+	; move into expected zp locations
 	sta	HGR_Y							; 3
 	stx	HGR_X							; 3
 	sty	HGR_X+1							; 3
+								;===========
+								;         9
+
+	; calc y-position addr.  no lookup table?
 	pha								; 3
 	and	#$C0							; 2
 	sta	GBASL							; 3
@@ -95,9 +101,6 @@ hposn:
 	ora	GBASL							; 3
 	sta	GBASL							; 3
 	pla								; 4
-								;===========
-								;	 31
-	; F423
 	sta	GBASH							; 3
 	asl								; 2
 	asl								; 2
@@ -112,24 +115,98 @@ hposn:
 	ora	HGR_PAGE						; 3
 	sta	GBASH							; 3
 								;============
-								;	 39
+								;	 61
 	; F438
-	txa								; 2
-	cpy	#0							; 2
-	beq	hposn_2							; 3
+	; divide/mod 16-bit x poisition by 7
+	; incoming, X=(y,x)
+	; outgoing y=q, a=r
+
+	; Divide by 7 (From December '84 Apple Assembly Line)
+
+	txa
+	clc
+	sta	HGR_HORIZ
+	lsr
+	lsr
+	lsr
+	adc	HGR_HORIZ
+	ror
+	lsr
+	lsr
+	adc	HGR_HORIZ
+	ror
+	lsr
+	lsr
+	; x/7 is in A
+
+	; calculate remainder
+	clc
+	sta	HGR_HORIZ
+	asl
+	adc	HGR_HORIZ
+	asl
+	adc	HGR_HORIZ
+	; HGR_HORIZ=x/7, A=HGR_HORIZ*7
+
+	; calculate remainder by X-(Q*7)
+	sec
+	eor	#$ff
+	adc	HGR_X
+	; A = remainder
+
+	cpy	#0
+	beq	only_low
+theres_high:
+
+	clc
+	adc	#4		; make remainder match
+	pha
+	lda	HGR_HORIZ
+	adc	#36
+	sta	HGR_HORIZ
+	pla
+only_low:
+	cmp	#7
+	bcc	done_mod	; blt
+
+	sec
+	sbc	#7
+	inc	HGR_HORIZ
+
+done_mod:
+
+
+;	txa								; 2
+;	cpy	#0							; 2
+;	beq	hposn_2							; 3
 									; -1
-	ldy	#35							; 2
-	adc	#4							; 2
-hposn_1:
-	iny								; 2
+;	ldy	#35							; 2
+;	adc	#4							; 2
+;hposn_1:
+;	iny								; 2
 	; f442
-hposn_2:
-	sbc	#7							; 2
-	bcs	hposn_1							; 3
+;hposn_2:
+;	sbc	#7							; 2
+;	bcs	hposn_1							; 3
 									; -1
-	sty	HGR_HORIZ						; 3
+	ldy	HGR_HORIZ
+;	sty	HGR_HORIZ						; 3
 	tax								; 2
-	lda	msktbl-$100+7,x		; LDA MSKTBL-$100+7,X  BIT MASK	; 4?
+	lda	msktbl,x		; 
+;	lda	msktbl-$100+7,x		; LDA MSKTBL-$100+7,X  BIT MASK	; 4?
+					; weird two's complement?
+
+					; if x=-6 = 249 = fa
+					; F5b2 - 1000 = f4b2
+					; f4b2+7 = f4b9
+					; -1 ff + f4b9 = f5b8 C0 6
+					; -2 fe + f4b9 = f5b7 A0 5
+					; -3 fd + f4b9 = f5b6 90 4
+					; -4 fc + f4b9 = f5b5 88 3
+					; -5 fb + f4b9 = f5b4 84 2
+					; -6 fa + f4b9 = f5b3 82 1
+					; -7 f9 + f4b9 = f5b2 81 0
+
 					; MSKTBL=F5B2
 	sta	HMASK							; 3
 	tya								; 2

gr-sim/6502_emulate.c

@@ -423,6 +423,24 @@ void txa(void) {
 	a=x;
 }
 
+void eor(int value) {
+
+	int temp_a;
+	int temp_value;
+	int result;
+
+	temp_a=a&0xff;
+	temp_value=value&0xff;
+
+	result=(temp_a^temp_value);
+
+	n=(result&0x80)>>7;
+
+	a=result&0xff;
+	z=(a==0);
+
+}
+
 unsigned char high(int value) {
 	return (value>>8)&0xff;
 }

gr-sim/6502_emulate.h

@@ -8,6 +8,7 @@ unsigned short y_indirect(unsigned char base, unsigned char y);
 int init_6502(void);
 void adc(int value);
 void sbc(int value);
+void eor(int value);
 void cmp(int value);
 void cpy(int value);
 void cpx(int value);
@@ -39,6 +40,7 @@ void ldx_const(int value);
 void ldy(int addr);
 void ldy_const(int value);
 void sta(int addr);
+void inc_mem(int addr);
 
 unsigned char high(int value);
 unsigned char low(int value);

gr-sim/hgr/seven.c

@@ -6,7 +6,7 @@
 #include "6502_emulate.h"
 #include "gr-sim.h"
 
-#define TEMP_Q	0xff
+#define HGR_HORIZ	0xff
 #define TEMP_R	0xfe
 
 static void fancy_div(int d, int *q, int *r) {
@@ -15,7 +15,7 @@ static void fancy_div(int d, int *q, int *r) {
 	//;15 bytes, 27 cycles
 
 	// y=xhigh x=xlow a=??
-	// q in y, r in x
+	// q in y, r in a
 
 	y=(d>>8)&0xff;
 	x=d&0xff;
@@ -25,52 +25,62 @@ static void fancy_div(int d, int *q, int *r) {
 	sta(TEMP_R);
 
 	c=0;
-	sta(TEMP_Q);		// 0
+	sta(HGR_HORIZ);		// 0
 	lsr();			// 0
 	lsr();			// 0
 	lsr();			// 0
-	adc_mem(TEMP_Q);	// 0
+	adc_mem(HGR_HORIZ);	// 0
 	ror();			// 0
 	lsr();			// 0
 	lsr();			// 0
-	adc_mem(TEMP_Q);	// 0
+	adc_mem(HGR_HORIZ);	// 0
 	ror();			// 0
 	lsr();			// 0
 	lsr();			// 0
 
+	// calc remainder
+
 	c=0;
-	sta(TEMP_Q);
+	sta(HGR_HORIZ);
 	asl();
-	adc_mem(TEMP_Q);
+	adc_mem(HGR_HORIZ);
 	asl();
-	adc_mem(TEMP_Q);
+	adc_mem(HGR_HORIZ);
+	// HGR_HORIZ=x/7, A=HGR_HORIZ*7
+
 
 	c=1;
-	sta(TEMP_R);
-	txa();
-	sbc_mem(TEMP_R);
-	tax();
+	eor(0xff);
+//	printf("%d+%d=",d&0xff,a);
+	adc(d&0xff);
+//	printf("%d\n",a);
+
+
+//	sta(TEMP_R);
+//	txa();
+//	sbc_mem(TEMP_R);
+//	tax();
 
 	if (y) {
-		x+=4;
-		lda(TEMP_Q);
 		c=0;
+		adc(4);
+		pha();
+		lda(HGR_HORIZ);
 		adc(36);
-		sta(TEMP_Q);
+		sta(HGR_HORIZ);
+		pla();
 	}
 
-	y=ram[TEMP_Q];
-
-	if (x>6) {
+	if (a>6) {
 		c=1;
-		txa();
 		sbc(7);
-		tax();
-		y++;
+		ram[HGR_HORIZ]++;
 	}
 
+	y=ram[HGR_HORIZ];
+
 	*q=y;
-	*r=x;
+	*r=a;
 }