From 78d3f650b2ca507e3d5376d3cad4d93df1901569 Mon Sep 17 00:00:00 2001
From: alekseiplusplus <alekseijeaves@protonmail.com>
Date: Sun, 3 Dec 2023 21:03:44 +1100
Subject: making CPU more correct, STILL not working

---
 src/cpu/instructions.c | 94 +++++++++++++++++++++++---------------------------
 1 file changed, 44 insertions(+), 50 deletions(-)

(limited to 'src/cpu/instructions.c')

diff --git a/src/cpu/instructions.c b/src/cpu/instructions.c
index 2a2f97f..5f4000a 100644
--- a/src/cpu/instructions.c
+++ b/src/cpu/instructions.c
@@ -19,14 +19,19 @@ AddData idata;
 void fLDA(Addressing addr, address val){
 	acc = idata.value;
 	SetFlagN(acc);
+	SetFlagZ(acc);
 }
 
 void fLDX(Addressing addr, address val){
 	X = idata.value;
+	SetFlagN(X);
+	SetFlagZ(X);
 }
 
 void fLDY(Addressing addr, address val){
 	Y = idata.value;
+	SetFlagN(Y);
+	SetFlagZ(Y);
 }
 
 void fSTA(Addressing addr, address val){
@@ -44,29 +49,25 @@ void fSTY(Addressing addr, address val){
 // Arithmetic Instructions
 
 void fADC(Addressing addr, address val){
-	int buffer = (int)acc + idata.value;
-	SetFlagV(buffer, acc);
+	byte buffer = acc + idata.value + getFlag(flag_C);
 
-	if (buffer > 255)
-		flagSet(flag_C);
-	else
-		flagClear(flag_C);
+	SetFlagV(buffer, acc);
 
-	acc += idata.value;
+	SetFlag(flag_C, (buffer < acc) ? 1 : 0);
+	
+	acc = buffer;
 	SetFlagN(acc);
 	SetFlagZ(acc);
 }
 
 void fSBC(Addressing addr, address val){
-	int buffer = acc - idata.value;
+	byte buffer = acc - idata.value - !getFlag(flag_C);
+        
 	SetFlagV(buffer, acc);
 
-	if (buffer < 0)
-		flagSet(flag_C);
-	else
-		flagClear(flag_C);
+	SetFlag(flag_C, (buffer > acc) ? 1 : 0);
 
-	acc -= idata.value;
+	acc = buffer;
 	SetFlagN(acc);
 	SetFlagZ(acc);
 }
@@ -75,10 +76,9 @@ void fSBC(Addressing addr, address val){
 
 void fINC(Addressing addr, address val){
 	byte a = GetMemory(idata.add);
-	a++;
-	SetMemory(idata.add, a);
-	SetFlagN(Memory[idata.add]);
-	SetFlagZ(Memory[idata.add]);
+	SetMemory(idata.add, ++a);
+	SetFlagN(a);
+	SetFlagZ(a);
 }
 
 void fINX(Addressing addr, address val){
@@ -95,10 +95,9 @@ void fINY(Addressing addr, address val){
 
 void fDEC(Addressing addr, address val){
 	byte a = GetMemory(idata.add);
-	a--;
-	SetMemory(idata.add, a);
-	SetFlagN(Memory[idata.add]);
-	SetFlagZ(Memory[idata.add]);
+	SetMemory(idata.add, --a);
+	SetFlagN(a);
+	SetFlagZ(a);
 }
 
 void fDEX(Addressing addr, address val){
@@ -136,7 +135,7 @@ void fEOR(Addressing addr, address val){
 // Jump, Branch, Compare, and Test Bits
 
 void fJMP(Addressing addr, address val){
-	PC = val; PC -= 2;
+	PC = idata.add - idata.length;
 }
 
 void fBCC(Addressing addr, address val){
@@ -172,38 +171,33 @@ void fBVC(Addressing addr, address val){
 }
 
 void fCMP(Addressing addr, address val){
-	SetFlag(flag_C, (acc >= val) ? 1 : 0);
-	SetFlag(flag_Z, (acc == val) ? 1 : 0);
-	SetFlag(flag_N, (acc  & flag_N     ) ? 1 : 0);
+	SetFlag(flag_C, (acc >= idata.value) ? 1 : 0);
+	SetFlag(flag_Z, (acc == idata.value) ? 1 : 0);
+	SetFlag(flag_N, (acc  < idata.value) ? 1 : 0);
 }
 
 void fCPX(Addressing addr, address val){
-	SetFlag(flag_C, (X >= val) ? 1 : 0);
-	SetFlag(flag_Z, (X == val) ? 1 : 0);
-	SetFlag(flag_N, (X  & flag_N     ) ? 1 : 0);
+	SetFlag(flag_C, (X >= idata.value) ? 1 : 0);
+	SetFlag(flag_Z, (X == idata.value) ? 1 : 0);
+	SetFlag(flag_N, (X  < idata.value) ? 1 : 0);
 }
 
 void fCPY(Addressing addr, address val){
-	SetFlag(flag_C, (Y >= val) ? 1 : 0);
-	SetFlag(flag_Z, (Y == val) ? 1 : 0);
-	SetFlag(flag_N, (Y  & flag_N     ) ? 1 : 0);
+	SetFlag(flag_C, (Y >= idata.value) ? 1 : 0);
+	SetFlag(flag_Z, (Y == idata.value) ? 1 : 0);
+	SetFlag(flag_N, (Y  < idata.value) ? 1 : 0);
 }
 
 void fBIT(Addressing addr, address val){
-	SetFlag(flag_N, (idata.value & flag_N)?1:0);
-	SetFlag(flag_V, (idata.value & flag_V)?1:0);
-	
-	if (((idata.value & flag_N) & (idata.value & flag_V)) == 0) {
-		flagSet(flag_Z);
-	} else {
-		flagSet(flag_Z);
-	}
+	SetFlag(flag_N, (idata.value & flag_N) ? 1 : 0);
+	SetFlag(flag_V, (idata.value & flag_V) ? 1 : 0);
+	SetFlag(flag_Z, (idata.value & acc)    ? 0 : 1);
 }
 
 // Shift and Rotate Instructions
 
 void fASL(Addressing addr, address val){
-	SetFlag(flag_C, (idata.value & 0x80)?1:0);
+	SetFlag(flag_C, (idata.value & 0x80));
 	acc = (idata.value << 1);
 	SetFlagN(acc);
 	SetFlagZ(acc);
@@ -217,16 +211,16 @@ void fLSR(Addressing addr, address val){
 }
 
 void fROL(Addressing addr, address val){
-	SetFlag(flag_C, (val & 0x80)?1:0);
-	acc = (val << 1);
+	SetFlag(flag_C, (idata.value & 0x80));
+	acc = (idata.value << 1);
 	acc |= (getFlag(flag_C)?1:0);
 	SetFlagN(acc);
 	SetFlagZ(acc);
 }
 
 void fROR(Addressing addr, address val){
-	SetFlag(flag_C, (val & 0x01));
-	acc = (val >> 1);
+	SetFlag(flag_C, (idata.value & 0x01));
+	acc = (idata.value >> 1);
 	acc |= (getFlag(flag_C)?0x80:0);
 	SetFlagN(acc);
 	SetFlagZ(acc);
@@ -236,14 +230,14 @@ void fROR(Addressing addr, address val){
 
 void fTAX(Addressing addr, address val){
 	X = acc;
-	//SetFlagN(X);
-	//SetFlagZ(X);
+	SetFlagN(X);
+	SetFlagZ(X);
 }
 
 void fTAY(Addressing addr, address val){
 	Y = acc;
-	//SetFlagN(Y);
-	//SetFlagZ(Y);
+	SetFlagN(Y);
+	SetFlagZ(Y);
 }
 
 void fTXA(Addressing addr, address val){
@@ -285,7 +279,6 @@ void fPLP(Addressing addr, address val){
 }
 
 // Subroutine Instructions
-// NEED TO FINISH THESE
 
 void fJSR(Addressing addr, address val){
 	SetStack((PC+3) >> 8);
@@ -294,8 +287,9 @@ void fJSR(Addressing addr, address val){
 }
 
 void fRTS(Addressing addr, address val){
-	PC  =  (address)(GetStack()) - 1;
+	PC  =  (address)(GetStack());
 	PC += ((address)(GetStack())) << 8;
+	PC -= 1;
 }
 
 void fRTI(Addressing addr, address val){
-- 
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