Decode ld r8, [hl] opcode

This opcode is treated differently from ld r8, n8
because it requires an extra machine cycle to pull
data from memory.

src/cpu.rs

@@ -88,6 +88,7 @@ impl SharpSM83 {
             Opcode::NOP => self.no_op(),
             Opcode::LDRI8(dest) => self.ld_r_n8(dest, bus),
             Opcode::Unimplemented(_) => {}
+            _ => {}
         }
     }
 

src/opcode.rs

@@ -22,6 +22,7 @@
 pub enum Opcode {
     NOP,
     LDRI8(Dest8Bit),
+    LdR8HLAddr,
     Unimplemented(u8),
 }
 
@@ -39,7 +40,11 @@ impl Opcode {
             (0b00000000, 0b00000110) => {
                 let reg_num = (data & 0b00111000) >> 3;
                 let register = Dest8Bit::from_u8(reg_num);
-                Opcode::LDRI8(register)
+                if register == Dest8Bit::HLAddr {
+                    Opcode::LdR8HLAddr
+                } else {
+                    Opcode::LDRI8(register)
+                }
             }
             _ => Opcode::Unimplemented(data),
         }
@@ -125,6 +130,12 @@ mod tests {
         assert_eq!(opcode, Opcode::LDRI8(destination));
     }
 
+    #[test]
+    fn should_return_ld_r8_addr_hl_given_00110110() {
+        let opcode = Opcode::decode(0b00110110);
+        assert_eq!(opcode, Opcode::LdR8HLAddr);
+    }
+
     #[test]
     fn should_return_b_when_given_0() {
         let register = Dest8Bit::from_u8(0);