Fixed ADC and SBC in decimal mode. All tests pass.

execute.go

@@ -221,43 +221,58 @@ func buildOpLogic(operation func(uint8, uint8) uint8) opFunc {
 
 func opADC(s *state, line []uint8, opcode opcode) {
 	value, _, _ := resolve(s, line, opcode)
-	if s.registers.getFlag(flagD) {
+	aValue := s.registers.getA()
-		// TODO BCD. See http://www.6502.org/tutorials/decimal_mode.html
+	carry := s.registers.getFlagBit(flagC)
-		panic("BCD not supported")
-	} else {
-		total := uint16(s.registers.getA()) +
-			uint16(value) +
-			uint16(s.registers.getFlagBit(flagC))
-		signedTotal := int16(int8(s.registers.getA())) +
-			int16(int8(value)) +
-			int16(s.registers.getFlagBit(flagC))
-		truncated := uint8(total)
 
+	total := uint16(aValue) + uint16(value) + uint16(carry)
+	signedTotal := int16(int8(aValue)) + int16(int8(value)) + int16(carry)
+	truncated := uint8(total)
+
+	if s.registers.getFlag(flagD) {
+		totalBcdLo := int(aValue&0x0f) + int(value&0x0f) + int(carry)
+		totalBcdHi := int(aValue>>4) + int(value>>4)
+		if totalBcdLo >= 10 {
+			totalBcdHi++
+		}
+		totalBcd := (totalBcdHi%10)<<4 + (totalBcdLo % 10)
+		s.registers.setA(uint8(totalBcd))
+		s.registers.updateFlag(flagC, totalBcdHi > 9)
+	} else {
 		s.registers.setA(truncated)
-		s.registers.updateFlagZN(truncated)
 		s.registers.updateFlag(flagC, total > 0xFF)
-		s.registers.updateFlag(flagV, signedTotal < -128 || signedTotal > 127)
 	}
+
+	// ZNV flags behave for BCD as if the operation was binary?
+	s.registers.updateFlagZN(truncated)
+	s.registers.updateFlag(flagV, signedTotal < -128 || signedTotal > 127)
 }
 
 func opSBC(s *state, line []uint8, opcode opcode) {
 	value, _, _ := resolve(s, line, opcode)
+	aValue := s.registers.getA()
+	carry := s.registers.getFlagBit(flagC)
+
+	total := 0x100 + uint16(aValue) - uint16(value) + uint16(carry) - 1
+	signedTotal := int16(int8(aValue)) - int16(int8(value)) + int16(carry) - 1
+	truncated := uint8(total)
+
 	if s.registers.getFlag(flagD) {
-		// TODO BCD
+		totalBcdLo := 10 + int(aValue&0x0f) - int(value&0x0f) + int(carry) - 1
-		panic("BCD not supported")
+		totalBcdHi := 10 + int(aValue>>4) - int(value>>4)
+		if totalBcdLo < 10 {
+			totalBcdHi--
+		}
+		totalBcd := (totalBcdHi%10)<<4 + (totalBcdLo % 10)
+		s.registers.setA(uint8(totalBcd))
+		s.registers.updateFlag(flagC, totalBcdHi >= 10)
 	} else {
-		total := 0x100 + uint16(s.registers.getA()) -
-			uint16(value) +
-			uint16(s.registers.getFlagBit(flagC)) - 1
-		signedTotal := int16(int8(s.registers.getA())) -
-			int16(int8(value)) +
-			int16(s.registers.getFlagBit(flagC)) - 1
-		truncated := uint8(total)
 		s.registers.setA(truncated)
-		s.registers.updateFlagZN(truncated)
 		s.registers.updateFlag(flagC, total > 0xFF)
-		s.registers.updateFlag(flagV, signedTotal < -128 || signedTotal > 127)
 	}
+
+	// ZNV flags behave for SBC as if the operation was binary
+	s.registers.updateFlagZN(truncated)
+	s.registers.updateFlag(flagV, signedTotal < -128 || signedTotal > 127)
 }
 
 const stackAddress uint16 = 0x0100

execute_test.go

@@ -268,30 +268,65 @@ func TestAdd(t *testing.T) {
 	s.registers.clearFlag(flagC)
 	executeLine(&s, []uint8{0x69, 0x0B})
 	if s.registers.getA() != 0xAB {
-		t.Errorf("Error in ADC A0 + 0B. %v", s.registers)
+		t.Errorf("Error in ADC. %v", s.registers)
 	}
 	if s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry ADC A0 + 0B. %v", s.registers)
+		t.Errorf("Error in carry ADC. %v", s.registers)
 	}
 
 	s.registers.setA(0xFF)
 	s.registers.clearFlag(flagC)
 	executeLine(&s, []uint8{0x69, 0x02})
 	if s.registers.getA() != 0x01 {
-		t.Errorf("Error in ADC A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in ADC with carry. %v", s.registers)
 	}
 	if !s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry ADC A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carry ADC with carry. %v", s.registers)
 	}
 
 	s.registers.setA(0xA0)
 	s.registers.setFlag(flagC)
 	executeLine(&s, []uint8{0x69, 0x01})
 	if s.registers.getA() != 0xA2 {
-		t.Errorf("Error in ADC C + A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carried ADC with carry. %v", s.registers)
 	}
 	if s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry ADC C + A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carry in carried ADC with carry. %v", s.registers)
+	}
+}
+
+func TestAddDecimal(t *testing.T) {
+	var s state
+	s.registers.setFlag(flagD)
+
+	s.registers.setA(0x12)
+	s.registers.clearFlag(flagC)
+	executeLine(&s, []uint8{0x69, 0x013})
+	if s.registers.getA() != 0x25 {
+		t.Errorf("Error in ADC decimal. %v", s.registers)
+	}
+	if s.registers.getFlag(flagC) {
+		t.Errorf("Error in carry ADC. %v", s.registers)
+	}
+
+	s.registers.setA(0x44)
+	s.registers.clearFlag(flagC)
+	executeLine(&s, []uint8{0x69, 0x68})
+	if s.registers.getA() != 0x12 {
+		t.Errorf("Error in ADC decimal  with carry. %v", s.registers)
+	}
+	if !s.registers.getFlag(flagC) {
+		t.Errorf("Error in carry ADC decimal with carry. %v", s.registers)
+	}
+
+	s.registers.setA(0x44)
+	s.registers.setFlag(flagC)
+	executeLine(&s, []uint8{0x69, 0x23})
+	if s.registers.getA() != 0x68 {
+		t.Errorf("Error in carried ADC decimal with carry. %v", s.registers)
+	}
+	if s.registers.getFlag(flagC) {
+		t.Errorf("Error in carry in carried ADC decimal with carry. %v", s.registers)
 	}
 }
 
@@ -301,31 +336,31 @@ func TestSub(t *testing.T) {
 	s.registers.setA(0x09)
 	s.registers.clearFlag(flagC)
 	executeLine(&s, []uint8{0xE9, 0x05})
-	if s.registers.getA() != 0x04 {
+	if s.registers.getA() != 0x03 {
-		t.Errorf("Error in SBC A0 + 0B. %v", s.registers)
+		t.Errorf("Error in SBC. %v", s.registers)
 	}
-	if s.registers.getFlag(flagC) {
+	if !s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry SBC A0 + 0B. %v", s.registers)
+		t.Errorf("Error in carry SBC. %v", s.registers)
 	}
 
 	s.registers.setA(0x01)
 	s.registers.clearFlag(flagC)
 	executeLine(&s, []uint8{0xE9, 0x02})
-	if s.registers.getA() != 0xFF {
+	if s.registers.getA() != 0xFE {
-		t.Errorf("Error in SBC A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in SBC with carry. %v", s.registers)
 	}
-	if !s.registers.getFlag(flagC) {
+	if s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry SBC A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carry SBC with carry. %v", s.registers)
 	}
 
 	s.registers.setA(0x08)
 	s.registers.setFlag(flagC)
 	executeLine(&s, []uint8{0xE9, 0x02})
-	if s.registers.getA() != 0x05 {
+	if s.registers.getA() != 0x06 {
-		t.Errorf("Error in SBC C + A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carried SBC with carry. %v", s.registers)
 	}
-	if s.registers.getFlag(flagC) {
+	if !s.registers.getFlag(flagC) {
-		t.Errorf("Error in carry SBC C + A0 + 0B with carry. %v", s.registers)
+		t.Errorf("Error in carry in carried SBC with carry. %v", s.registers)
 	}
 
 }

main.go

@@ -8,19 +8,22 @@ func main() {
 
 	s.registers.setPC(0x0400)
 	for true {
-		for i := 0; i < 20; i++ {
+		testCase := s.memory[0x0200]
-			testCase := s.memory[0x0200]
+		if testCase >= 240 {
-			log := testCase > 41
+			break
-			if log {
+		}
-				fmt.Printf("[ %d ] ", testCase)
+		log := testCase > 43
-			}
+		if log {
-			pc := s.registers.getPC()
+			fmt.Printf("[ %d ] ", testCase)
-			executeInstruction(&s, log)
+		}
-			if pc == s.registers.getPC() {
+		pc := s.registers.getPC()
-				s.memory.printPage(0x00)
+		executeInstruction(&s, log)
-				//s.memory.printPage(0x01)
+		if pc == s.registers.getPC() {
-				panic("No change in PC")
+			//s.memory.printPage(0x00)
-			}
+			//s.memory.printPage(0x01)
+			panic("No change in PC")
 		}
 	}
+
+	fmt.Printf("Test completed\n")
 }