famiyirl: SBC absolute/imediat

Signed-off-by: Matthias Gatto <[email protected]>
cosmo-ray · Apr 28, 2024 · c7199d7 · c7199d7
1 parent 93156e4
commit c7199d7
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Showing 2 changed files with 29 additions and 3 deletions.
diff --git a/modules/famiyirl/init.c b/modules/famiyirl/init.c
@@ -450,7 +450,7 @@ static int process_inst(void)
 		char res = get_mem(addr);
 		int check_carry = cpu.a + res;
 
-		cpu.a += res;
+		cpu.a += res + (cpu.flag & CARY_FLAG);
 		SET_CARY(check_carry > 255);
 		SET_OVERFLOW(old_sign != (cpu.a & 0x80));
 		SET_NEGATIVE(!!(0x80 & cpu.a));
@@ -465,14 +465,39 @@ static int process_inst(void)
 
 		int check_carry = cpu.a + addr;
 
-		cpu.a += addr;
+		cpu.a += addr + (cpu.flag & CARY_FLAG);
 		SET_CARY(check_carry > 255);
 		SET_OVERFLOW(old_sign != (cpu.a & 0x80));
 		SET_NEGATIVE(!!(0x80 & cpu.a));
 		SET_ZERO(!cpu.a);
 		cpu.cycle_cnt += 2;
 	}
 	break;
+	case SBC_ab:
+	case SBC_im:
+	{
+	  char res;
+	  if (opcode == SBC_ab) {
+		int addr = get_mem(++cpu.pc);
+
+		addr |= get_mem(++cpu.pc) << 8;
+		res = get_mem(addr);
+		cpu.cycle_cnt += 2;
+	  } else {
+	    res = get_mem(++cpu.pc);
+
+	  }
+		char old_sign = cpu.a & 0x80;
+		int check_carry = cpu.a - res - 1 + (cpu.flag & CARY_FLAG);
+
+		cpu.a -= res;
+		SET_CARY(check_carry >= 0);
+		SET_OVERFLOW(old_sign != (cpu.a & 0x80));
+		SET_NEGATIVE(!!(0x80 & cpu.a));
+		SET_ZERO(!cpu.a);
+		cpu.cycle_cnt += 2;
+	}
+	break;
 	case LDA_addx:
 	{
 		unsigned char base_addr =  get_mem(++cpu.pc);

diff --git a/modules/famiyirl/opcode.h b/modules/famiyirl/opcode.h
@@ -61,7 +61,8 @@
   OPCODE(BNE, 0xD0) //branch on not equal (zero clear)
   OPCODE(CLD, 0xD8) //clear decimal
   OPCODE(CPX, 0xE0) //compare with X
-  OPCODE(SBC, 0xE1) //subtract with carry
+  OPCODE(SBC_im, 0xE9) //subtract with carry
+  OPCODE(SBC_ab, 0xEd) //subtract with carry
   OPCODE(INX, 0xE8) //increment X
   OPCODE(NOP, 0xEA) //no operation
   OPCODE(CPX_var, 0xEC) //compare with X