diff --git a/src/state.rs b/src/state.rs
index 35e86d6..97fe804 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -15,6 +15,7 @@ pub struct EmuState {
     options: Options,
     fp_state: FrontpanelState,
     cards: Vec<(&'static Type, Box<dyn Card>)>,
+    io_cache: Option<(u8, u8)>
 }
 
 impl EmuState {
@@ -34,6 +35,7 @@ impl EmuState {
             options,
             fp_state: FrontpanelState::default(),
             cards,
+            io_cache: None,
         };
         slf.apply_options();
         slf
@@ -125,8 +127,10 @@ impl EmuState {
             | MemCycle::Hlta => {
                 self.fp_state.set_data(0xff);
             }
-            MemCycle::In(_) => {
-                self.fp_state.set_data(0);
+            MemCycle::In(a) => {
+                let data = self.read_io(a as u8);
+                self.io_cache = Some((a as u8, data));
+                self.fp_state.set_data(data);
             }
             MemCycle::Inta(_) => todo!(),
             MemCycle::IntaHlt(_) => todo!(),
@@ -141,8 +145,22 @@ impl EmuState {
                 self.write_mem(a, d);
                 0
             }
-            MemCycle::In(_) => 0,
-            MemCycle::Out(_, _) => 0,
+            MemCycle::In(a) => {
+                if let Some((cached_addr, cached_data)) = self.io_cache {
+                    if cached_addr == a as u8 {
+                        self.io_cache = None;
+                        cached_data
+                    } else {
+                        self.read_io(a as u8)
+                    }
+                } else {
+                    self.read_io(a as u8)
+                }
+            },
+            MemCycle::Out(a, d) => {
+                self.write_io(a as u8, d);
+                0
+            },
             MemCycle::Inta(_) => todo!(),
             MemCycle::Hlta => {
                 self.running = false;
@@ -217,4 +235,12 @@ impl EmuState {
     fn write_mem(&mut self, address: u16, data: u8) {
         self.cards.iter_mut().find_map(|(_, card)| card.write_mem(address, data));
     }
+
+    fn read_io(&mut self, address: u8) -> u8 {
+        self.cards.iter_mut().find_map(|(_, card)| card.read_io(address)).unwrap_or(0xFF)
+    }
+
+    fn write_io(&mut self, address: u8, data: u8) {
+        self.cards.iter_mut().find_map(|(_, card)| card.write_io(address, data));
+    }
 }