From f9e82a43d6b58149f234dc1544c8cfee32cf3310 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sat, 8 Sep 2018 23:52:58 -0400
Subject: [PATCH] gr-sim: work on getting a div by 7 working

---
 gr-sim/6502_emulate.c | 57 +++++++++++++++++++++++++
 gr-sim/6502_emulate.h |  3 ++
 gr-sim/hgr/Makefile   | 11 ++++-
 gr-sim/hgr/seven.c    | 98 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 167 insertions(+), 2 deletions(-)
 create mode 100644 gr-sim/hgr/seven.c

diff --git a/gr-sim/6502_emulate.c b/gr-sim/6502_emulate.c
index 1bc51d86..7dbe8bb3 100644
--- a/gr-sim/6502_emulate.c
+++ b/gr-sim/6502_emulate.c
@@ -62,6 +62,27 @@ void adc(int value) {
 
 }
 
+void adc_mem(int addr) {
+
+	int temp_a;
+	int temp_value;
+	int result;
+
+	temp_a=a&0xff;
+	temp_value=ram[addr]&0xff;
+
+	result=(temp_a+temp_value+c);
+
+	c=(result&0x100)>>8;
+	n=(result&0x80)>>7;
+
+	v=!!((a^result)&(temp_value^result)&0x80);
+
+	a=result&0xff;
+	z=(a==0);
+
+}
+
 void sbc(int value) {
 	int temp_a;
 	int result;
@@ -83,6 +104,29 @@ void sbc(int value) {
 	z=(a==0);
 
 
+}
+
+void sbc_mem(int addr) {
+	int temp_a;
+	int result;
+	int temp_value;
+
+	temp_a=a&0xff;
+	temp_value=(~ram[addr])&0xff;
+
+	result=temp_a+temp_value+c;
+
+//	printf("SBC: %x - %x (%x) = %x\n",a,value,c,result);
+
+	c=(result&0x100)>>8;
+	n=(result&0x80)>>7;
+
+	v=!!((a^result)&((255-ram[addr])^result)&0x80);
+
+	a=result&0xff;
+	z=(a==0);
+
+
 }
 
 void cmp(int value) {
@@ -366,6 +410,19 @@ void ldy_const(int value) {
 	n=!!(y&0x80);
 }
 
+void sta(int addr) {
+
+	ram[addr]=a;
+}
+
+void tax(void) {
+	x=a;
+}
+
+void txa(void) {
+	a=x;
+}
+
 unsigned char high(int value) {
 	return (value>>8)&0xff;
 }
diff --git a/gr-sim/6502_emulate.h b/gr-sim/6502_emulate.h
index cbbc01fe..78f012ce 100644
--- a/gr-sim/6502_emulate.h
+++ b/gr-sim/6502_emulate.h
@@ -17,6 +17,8 @@ void lsr(void);
 void asl(void);
 void ror(void);
 void rol(void);
+void adc_mem(int addr);
+void sbc_mem(int addr);
 void asl_mem(int addr);
 void ror_mem(int addr);
 void rol_mem(int addr);
@@ -36,6 +38,7 @@ void ldx(int addr);
 void ldx_const(int value);
 void ldy(int addr);
 void ldy_const(int value);
+void sta(int addr);
 
 unsigned char high(int value);
 unsigned char low(int value);
diff --git a/gr-sim/hgr/Makefile b/gr-sim/hgr/Makefile
index c4acda29..bc40ee0d 100644
--- a/gr-sim/hgr/Makefile
+++ b/gr-sim/hgr/Makefile
@@ -6,7 +6,7 @@ SDL_LIBS= `sdl-config --libs`
 SDL_INCLUDE= `sdl-config --cflags`
 GR_SIM = ../gr-sim.a
 
-all:	fireworks fw_purple lines image_load hgr_view
+all:	fireworks fw_purple lines image_load hgr_view seven
 
 ###
 
@@ -47,9 +47,16 @@ fw_purple:	fw_purple.o $(GR_SIM)
 
 fw_purple.o:	fw_purple.c
 	$(CC) $(CFLAGS) -c fw_purple.c
+###
+
+seven:	seven.o $(GR_SIM)
+	$(CC) $(LFLAGS) $(SDL_LIBS) -o seven seven.o $(GR_SIM)
+
+seven.o:	seven.c
+	$(CC) $(CFLAGS) -c seven.c
 
 ####
 
 
 clean:	
-	rm -f *~ *.o fireworks lines image_load hgr_view fw_purple
+	rm -f *~ *.o fireworks lines image_load hgr_view fw_purple seven
diff --git a/gr-sim/hgr/seven.c b/gr-sim/hgr/seven.c
new file mode 100644
index 00000000..671585a3
--- /dev/null
+++ b/gr-sim/hgr/seven.c
@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <math.h>
+
+#include "6502_emulate.h"
+#include "gr-sim.h"
+
+#define TEMP_Q	0xff
+#define TEMP_R	0xfe
+
+static void fancy_div(int d, int *q, int *r) {
+
+	//;Divide by 7 (From December '84 Apple Assembly Line)
+	//;15 bytes, 27 cycles
+
+	// y=xhigh x=xlow a=??
+	// q in y, r in x
+
+	y=(d>>8)&0xff;
+	x=d&0xff;
+
+	a=x;
+
+	sta(TEMP_R);
+
+	c=0;
+	sta(TEMP_Q);		// 0
+	lsr();			// 0
+	lsr();			// 0
+	lsr();			// 0
+	adc_mem(TEMP_Q);	// 0
+	ror();			// 0
+	lsr();			// 0
+	lsr();			// 0
+	adc_mem(TEMP_Q);	// 0
+	ror();			// 0
+	lsr();			// 0
+	lsr();			// 0
+
+	c=0;
+	sta(TEMP_Q);
+	asl();
+	adc_mem(TEMP_Q);
+	asl();
+	adc_mem(TEMP_Q);
+
+	c=1;
+	sta(TEMP_R);
+	txa();
+	sbc_mem(TEMP_R);
+	tax();
+
+	if (y) {
+		x+=4;
+		lda(TEMP_Q);
+		c=0;
+		adc(36);
+		sta(TEMP_Q);
+	}
+
+	y=ram[TEMP_Q];
+
+	if (x>6) {
+		c=1;
+		txa();
+		sbc(7);
+		tax();
+		y++;
+	}
+
+	*q=y;
+	*r=x;
+}
+
+
+int main(int argc, char **argv) {
+
+	int i,actual_q,actual_r;
+	int fancy_q,fancy_r;
+
+	grsim_init();
+
+	for(i=0;i<280;i++) {
+
+		fancy_div(i,&fancy_q,&fancy_r);
+
+		actual_q=i/7;
+		actual_r=i%7;
+
+		if ((fancy_q!=actual_q) || (fancy_r!=actual_r)) {
+			printf("%03x\t%d,%d\t%d,%d\n",
+				i,actual_q,actual_r,fancy_q,fancy_r);
+		}
+	}
+
+	return 0;
+}