initial code for the opcodes

src/6502.c

@@ -115,7 +115,7 @@ void execute()
         case EOR: return eor();
         case INC: return inc();
         case JMP: return jmp();
-        case JPA: return jmp();
+        case JPA: return jpa();
         case LDA: return lda();
         case LDX: return ldx();
         case LDY: return ldy();
@@ -132,7 +132,7 @@ void execute()
 
 void run()
 {
-    while (pc != 0)
+    while (1)
     {
         fetch();
         decode();

src/inc/opcodes.h

@@ -8,6 +8,7 @@ db ac; // accumulator
 db x;  // x register
 db y;  // y register
 db sp; // stack pointer
+db sr; // status register
 db ir; // intruction register
 
 enum opcodes_table
@@ -29,8 +30,7 @@ enum opcodes_list
     RTS = 0x60, BVS = 0x70, BCC = 0x90, BCS = 0xB0, BNE = 0xD0, BEQ = 0xF0,
     PHP = 0x08, CLC = 0x18, PLP = 0x28, SEC = 0x38, PHA = 0x48, CLI = 0x58, PLA = 0x68, SEI = 0x78,
     DEY = 0x88, TYA = 0x98, TAY = 0xA8, CLV = 0xB8, INY = 0xC8, CLD = 0xD8, INX = 0xE8, SED = 0xF8,
-    TXA = 0x8A, TXS = 0x9A, TAX = 0xAA, TSX = 0xBA, DEX = 0xCA, NOP = 0xEA,
-    XXX = 0xFF
+    TXA = 0x8A, TXS = 0x9A, TAX = 0xAA, TSX = 0xBA, DEX = 0xCA, NOP = 0xEA
 };
 
 enum address_mode
@@ -55,7 +55,7 @@ am address_mode;
 
 void adc(); // add memory to accumalator with carry
 void and(); // and memory with accumulator
-void asl(); // shift left one bit (memory on accumulator)
+void asl(); // shift left one bit (memory or accumulator)
 void bcc(); // branch on carry clear
 void bcs(); // branch on carry set
 void beq(); // branch on result zero
@@ -80,7 +80,8 @@ void eor(); // exclusive-or memory with accumulator
 void inc(); // increment memory by one
 void inx(); // increment index x by one
 void iny(); // increment index y by one
-void jmp(); // jump to new location
+void jmp(); // jump to new location (indirect)
+void jpa(); // jump to new location (absolute)
 void jsr(); // jump to new location saving return address
 void lda(); // load accumulator with memory
 void ldx(); // load index x with memory
@@ -110,4 +111,26 @@ void txa(); // transfer index x to accumulator
 void txs(); // transfer index x to stack pointer
 void tya(); // transfer index y to accumulator
 
+#define N_IS_SET    (sr & 0b10000000) // negative
+#define N_SET   sr = sr | 0b10000000
+#define N_UNSET sr = sr & 0b01111111
+#define V_IS_SET    (sr & 0b01000000) // overflow
+#define V_SET   sr = sr | 0b01000000
+#define V_UNSET sr = sr & 0b10111111
+#define B_IS_SET    (sr & 0b00010000) // break
+#define B_SET   sr = sr | 0b00010000
+#define B_UNSET sr = sr & 0b11101111
+#define D_IS_SET    (sr & 0b00001000) // decimal mode
+#define D_SET   sr = sr | 0b00001000
+#define D_UNSET sr = sr & 0b11110111
+#define I_IS_SET    (sr & 0b00000100) // interrupt disabled
+#define I_SET   sr = sr | 0b00000100
+#define I_UNSET sr = sr & 0b11111011
+#define Z_IS_SET    (sr & 0b00000010) // zero
+#define Z_SET   sr = sr | 0b00000010
+#define Z_UNSET sr = sr & 0b11111101
+#define C_IS_SET    (sr & 0b00000001) // carry
+#define C_SET   sr = sr | 0b00000001
+#define C_UNSET sr = sr & 0b11111110
+
 #endif

src/opcodes.c

@@ -70,31 +70,55 @@ void fetch_operand()
 void adc()
 {
     // add memory to accumalator with carry
+    fetch_operand();
+    ac = ac + operand + C_IS_SET;
 }
 
 void and()
 {
     // and memory with accumulator
+    fetch_operand();
+    ac = ac & operand;
 }
 
 void asl()
 {
-    // shift left one bit (memory on accumulator)
+    // shift left one bit (memory or accumulator)
+    fetch_operand();
+    operand = operand << 1;
 }
 
 void bcc()
 {
     // branch on carry clear
+    if(!C_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void bcs()
 {
     // branch on carry set
+    if(C_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void beq()
 {
     // branch on result zero
+    if(Z_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void bit()
@@ -105,16 +129,34 @@ void bit()
 void bmi()
 {
     // branch on result minus
+    if(N_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void bne()
 {
     // branch on result not zero
+    if(!Z_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void bpl()
 {
     // branch on result plus
+    if(!N_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void brk()
@@ -125,31 +167,47 @@ void brk()
 void bvc()
 {
     // branch on overflow clear
+    if(!V_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void bvs()
 {
     // branch on overflow set
+    if(V_IS_SET)
+    {
+        address = read_byte(pc);
+        address = address + pc;
+        pc = address;
+    }
 }
 
 void clc()
 {
     // clear carry flag
+    C_UNSET;
 }
 
 void cld()
 {
     // clear decimal mode
+    D_UNSET;
 }
 
 void cli()
 {
     // clear interrupt disable bit
+    I_UNSET;
 }
 
 void clv()
 {
     // clear overflow flag
+    V_UNSET;
 }
 
 void cmp()
@@ -190,21 +248,35 @@ void eor()
 void inc()
 {
     // increment memory by one
+    operand = operand + 1;
+    write_mem(address, operand); 
 }
 
 void inx()
 {
     // increment index x by one
+    x = x + 1;
 }
 
 void iny()
 {
     // increment index y by one
+    y = y + 1;
 }
 
 void jmp()
 {
-    // jump to new location
+    // jump to new location (indirect)
+    address = read_word(pc);
+    address = read_word(address);
+    pc = address;
+}
+
+void jpa()
+{
+    // jump to new location (absolute)
+    address = read_word(pc);
+    pc = address;
 }
 
 void jsr()