diff --git a/src/nes/cartridge.rs b/src/nes/cartridge.rs
index ff19382..a14eeac 100644
--- a/src/nes/cartridge.rs
+++ b/src/nes/cartridge.rs
@@ -112,21 +112,26 @@ impl Cartridge {
     pub fn writeb(&mut self, addr: Addr, data: Byte) -> bool {
         if let Some(mapped_addr) = self.mapper.map_write_addr(addr) {
             self.prg_rom[mapped_addr as usize] = data;
-            return true
+            return true;
         }
         false
     }
 
     // Read from cartridge if the cartridge has readable VRAM/VROM
     pub fn readb_ppu(&self, addr: Addr) -> Option<Byte> {
-        // TODO
+        if let Some(mapped_addr) = self.mapper.map_read_addr_ppu(addr) {
+            return Some(self.chr_rom[mapped_addr as usize])
+        }
         None
     }
 
     // Let the cartridge handle the ppu write. Returns true if cartridge
     // handled the write, false otherwise
     pub fn writeb_ppu(&mut self, addr: Addr, data: Byte) -> bool {
-        // TODO
+        if let Some(mapped_addr) = self.mapper.map_write_addr_ppu(addr) {
+            self.chr_rom[mapped_addr as usize] = data;
+            return true;
+        }
         false
     }
 }
diff --git a/src/nes/mappers.rs b/src/nes/mappers.rs
index a61b390..956512b 100644
--- a/src/nes/mappers.rs
+++ b/src/nes/mappers.rs
@@ -3,6 +3,8 @@ use crate::nes::types::*;
 pub trait Mapper {
     fn map_read_addr(&self, addr: Addr) -> Option<Addr>;
     fn map_write_addr(&self, addr: Addr) -> Option<Addr>;
+    fn map_read_addr_ppu(&self, addr: Addr) -> Option<Addr>;
+    fn map_write_addr_ppu(&self, addr: Addr) -> Option<Addr>;
 }
 
 // Mapper 0
@@ -49,4 +51,20 @@ impl Mapper for Mapper0 {
         }
         None
     }
+
+    fn map_read_addr_ppu(&self, addr: Addr) -> Option<Addr> {
+        if 0x0000 <= addr && addr <= 0x1FFF {
+            return Some(addr)
+        }
+        None
+    }
+
+    fn map_write_addr_ppu(&self, addr: Addr) -> Option<Addr> {
+        if 0x0000 <= addr && addr <= 0x1FFF {
+            if self.chr_banks == 0 {  // no banks => RAM
+                return Some(addr)
+            }
+        }
+        None
+    }
 }
diff --git a/src/nes/ppubus.rs b/src/nes/ppubus.rs
index 889d26e..4206e94 100644
--- a/src/nes/ppubus.rs
+++ b/src/nes/ppubus.rs
@@ -35,7 +35,13 @@ impl PPUBus {
 
 impl PPUMemory for PPUBus {
     fn readb_ppu(&self, addr: Addr) -> Byte {
-        // give the cartridge a chance to handle it
+        // Palette is never mapped to cartridge
+        if PALETTE_ADDR_RANGE[0] <= addr && addr <= PALETTE_ADDR_RANGE[1] {
+            let rel_addr = addr - 0x3F00;
+            return self.palette_memory[(rel_addr % 0x0020) as usize]
+        }
+
+        // give the cartridge a chance to handle the rest
         if let Some(cartridge) = &self.cartridge {
             if let Some(data) = cartridge.borrow().readb_ppu(addr) {
                 return data
@@ -59,15 +65,17 @@ impl PPUMemory for PPUBus {
             let rel_addr = addr - 0x2000;
             return self.nametable_memory[table][(rel_addr % 0x400) as usize]
         }
-        if PALETTE_ADDR_RANGE[0] <= addr && addr <= PALETTE_ADDR_RANGE[1] {
-            let rel_addr = addr - 0x3F00;
-            return self.palette_memory[(rel_addr % 0x0020) as usize]
-        }
-
+        
         0x00
     }
     fn writeb_ppu(&mut self, addr: Addr, data: Byte) {
-        // give the cartridge a chance to handle it
+        // Palette is never mapped to cartridge
+        if PALETTE_ADDR_RANGE[0] <= addr && addr <= PALETTE_ADDR_RANGE[1] {
+            let rel_addr = addr - 0x3F00;
+            self.palette_memory[(rel_addr % 0x0020) as usize] = data;
+        }
+
+        // give the cartridge a chance to handle the rest
         if let Some(cartridge) = &self.cartridge {
             if cartridge.borrow_mut().writeb_ppu(addr, data) {
                 return
@@ -91,10 +99,6 @@ impl PPUMemory for PPUBus {
             let rel_addr = addr - 0x2000;
             self.nametable_memory[table][(rel_addr % 0x400) as usize] = data;
         }
-        if PALETTE_ADDR_RANGE[0] <= addr && addr <= PALETTE_ADDR_RANGE[1] {
-            let rel_addr = addr - 0x3F00;
-            self.palette_memory[(rel_addr % 0x0020) as usize] = data;
-        }
     }
 }