set_low_a function

snes-core/src/cpu/instructions.rs

@@ -38,7 +38,7 @@ impl CPU {
                     true => alu::adc8bcd(target as u8, value, carry_flag),
                     false => alu::adc8bin(target as u8, value, carry_flag),
                 };
-                self.registers.a = (self.registers.a & 0xFF00) | (result as u16);
+                self.registers.set_low_a(result as u8);
                 self.registers.set_carry_flag(is_carry);
                 self.registers.set_negative_flag(is_negative);
                 self.registers.set_zero_flag(is_zero);
@@ -71,7 +71,7 @@ impl CPU {
                     true => alu::sbc8bcd(target as u8, value, carry_flag),
                     false => alu::sbc8bin(target as u8, value, carry_flag),
                 };
-                self.registers.a = (self.registers.a & 0xFF00) | (result as u16);
+                self.registers.set_low_a(result as u8);
                 self.registers.set_carry_flag(is_carry);
                 self.registers.set_negative_flag(is_negative);
                 self.registers.set_zero_flag(is_zero);

snes-core/src/cpu/registers.rs

@@ -27,6 +27,10 @@ impl Registers {
         }
     }
 
+    pub fn set_low_a(&mut self, val: u8) {
+        self.a = (self.a & 0xFF00) | (val as u16);
+    }
+
     pub fn get_carry_flag(&self) -> bool {
         (self.p & 0b0000_0001) == 1
     }
@@ -117,6 +121,14 @@ impl Registers {
 mod registers_tests {
     use super::*;
 
+    #[test]
+    fn test_set_low_a() {
+        let mut registers = Registers::new();
+        registers.a = 0xA1A1;
+        registers.set_low_a(0xFF);
+        assert_eq!(registers.a, 0xA1FF);
+    }
+
     #[test]
     fn test_get_pc_address() {
         let mut registers = Registers::new();