implement HALT

src/processor/mod.rs

@@ -29,6 +29,7 @@ pub struct CPU {
     pub last_instruction_addr: u16,
     pub window: Window,
     pub gpu: GPU,
+    halted: bool,
 }
 
 // Hz
@@ -45,10 +46,19 @@ impl CPU {
             last_instruction_addr: 0x0,
             window,
             gpu: GPU::default(),
+            halted: false,
         }
     }
 
     pub fn exec_next(&mut self) {
+        let interrupt_cycles = self.handle_interrupts();
+        self.increment_timers(interrupt_cycles);
+
+        if self.halted {
+            self.increment_timers(1);
+            return;
+        }
+
         self.last_instruction_addr = self.reg.pc;
         let opcode = self.next_opcode();
         self.last_instruction = opcode;
@@ -69,9 +79,6 @@ impl CPU {
         let cycles = self.run_opcode(opcode);
         self.memory.user_mode = false;
         self.increment_timers(cycles);
-
-        let interrupt_cycles = self.handle_interrupts();
-        self.increment_timers(interrupt_cycles);
     }
 
     fn increment_timers(&mut self, cycles: u8) {
@@ -149,6 +156,7 @@ impl CPU {
     }
 
     fn service_interrupt(&mut self, addr: u16) {
+        self.halted = false;
         self.push(self.reg.pc);
         self.reg.pc = addr;
         self.memory.ime = false;

src/processor/opcodes.rs

@@ -552,7 +552,8 @@ impl CPU {
                 2
             }
             0x76 => {
-                panic!("halt")
+                self.halted = true;
+                1
             }
             0x77 => {
                 self.memory.set(self.reg.hl, self.reg.get_8(Reg8::A));