Minor refactors and bug fixes

- Bit instruction now sets Z flag correctly
- DMA is no longer handled by cpu.rs

src/mem.rs

@@ -200,10 +200,8 @@ impl<R: Copy> MemoryMap<R> {
         }
         None
     }
-}
 
-impl<R> Memory for MemoryMap<R> {
-    fn peek(&self, addr: u16) -> Option<u8> {
+    fn peek_val(&self, addr: u16) -> Option<u8> {
         for segment in &self.segments {
             if segment.position <= addr && addr - segment.position < segment.size {
                 return match &segment.mem {
@@ -212,7 +210,7 @@ impl<R> Memory for MemoryMap<R> {
                     Data::Reg(_) => None,
                     Data::Mirror(pos) => {
                         let offset = addr - segment.position;
-                        self.peek(pos + offset)
+                        self.peek_val(pos + offset)
                     }
                     Data::Disabled => None,
                 };
@@ -220,6 +218,20 @@ impl<R> Memory for MemoryMap<R> {
         }
         None
     }
+}
+
+impl<R: Copy> Memory for MemoryMap<R> {
+    fn peek(&self, addr: usize) -> Option<u8> {
+        self.peek_val(addr as u16)
+    }
+
+    fn len(&self) -> usize {
+        self.segments
+            .iter()
+            .map(|s| s.position as usize + s.size as usize)
+            .max()
+            .unwrap_or(0)
+    }
 
     fn edit_ver(&self) -> usize {
         self.edit_ver
@@ -269,7 +281,7 @@ impl fmt::Display for SegmentId {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Mapped {
     cpu: MemoryMap<CPUMMRegisters>,
     ppu: MemoryMap<PPUMMRegisters>,
@@ -444,13 +456,13 @@ impl Mapped {
     }
 
     pub fn peek_ppu(&self, addr: u16) -> Option<u8> {
-        self.ppu.peek(addr)
+        self.ppu.peek_val(addr)
     }
     pub fn ppu_edit_ver(&self) -> usize {
         self.ppu.edit_ver
     }
     pub fn peek_cpu(&self, addr: u16) -> Option<u8> {
-        self.cpu.peek(addr)
+        self.cpu.peek_val(addr)
     }
     pub fn cpu_edit_ver(&self) -> usize {
         self.cpu.edit_ver
@@ -608,11 +620,7 @@ impl<'a> CpuMem<'a> {
             }
             Some((CPUMMRegisters::APU, offset, val)) => {
                 if offset == 0x014 {
-                    *self.dma = DmaState::Running {
-                        cpu_addr: (val as u16) << 8,
-                        rem: 0xFF,
-                        read: None,
-                    };
+                    *self.dma = DmaState::Idle((val as u16) << 8);
                 } else if offset == 0x16 {
                     self.controllers.write_joy_strobe(val);
                 } else {