diff --git a/Changes.txt b/Changes.txt
index 22eda9028..70c27806c 100644
--- a/Changes.txt
+++ b/Changes.txt
@@ -14,9 +14,16 @@
 
 3.7.2 to 3.8: (xxx xx, 2012)
 
+  * Note: because of TIA/RIOT changes, the state file format has changed
+          again, and old state files will not work with this release.
+
   * Improved handling of 'illegal' VSYNC signals, which sometimes created
     'short' frames that caused massive flickering.
 
+  * Improved emulation of RIOT chip, in particular the behaviour of
+    reading from TIMINT.  Also, D6 of the Interrupt Flag register is now
+    properly set on active transition of the PA7 pin.
+
   * The ROM properties database now uses 'Auto' instead of 'Auto-select'
     everywhere.  This makes for less typing when running from the
     commandline.
diff --git a/src/emucore/Control.hxx b/src/emucore/Control.hxx
index 63463058f..a79efd3fb 100644
--- a/src/emucore/Control.hxx
+++ b/src/emucore/Control.hxx
@@ -65,6 +65,7 @@ class Controller : public Serializable
   /**
     Riot debug class needs special access to the underlying controller state
   */
+  friend class M6532;
   friend class RiotDebug;
   friend class CompuMate;
 
diff --git a/src/emucore/EventHandler.cxx b/src/emucore/EventHandler.cxx
index 698f24119..246732c83 100644
--- a/src/emucore/EventHandler.cxx
+++ b/src/emucore/EventHandler.cxx
@@ -42,7 +42,7 @@
 #include "Snapshot.hxx"
 #include "Sound.hxx"
 #include "StateManager.hxx"
-#include "Switches.hxx"
+#include "M6532.hxx"
 #include "MouseControl.hxx"
 
 #include "EventHandler.hxx"
@@ -955,9 +955,7 @@ void EventHandler::poll(uInt64 time)
   // related to emulation
   if(myState == S_EMULATE)
   {
-    myOSystem->console().controller(Controller::Left).update();
-    myOSystem->console().controller(Controller::Right).update();
-    myOSystem->console().switches().update();
+    myOSystem->console().riot().update();
 
 #if 0
     // Now check if the StateManager should be saving or loading state
diff --git a/src/emucore/M6532.cxx b/src/emucore/M6532.cxx
index 7d2aeb6fb..e53bbc875 100644
--- a/src/emucore/M6532.cxx
+++ b/src/emucore/M6532.cxx
@@ -64,6 +64,9 @@ void M6532::reset()
   // Zero the interrupt flag register and mark D7 as invalid
   myInterruptFlag = 0x00;
   myTimerFlagValid = false;
+
+  // Edge-detect set to negative (high to low)
+  myEdgeDetectPositive = false;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -78,6 +81,29 @@ void M6532::systemCyclesReset()
   myConsole.controller(Controller::Right).systemCyclesReset();
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void M6532::update()
+{
+  Controller& port0 = myConsole.controller(Controller::Left);
+  Controller& port1 = myConsole.controller(Controller::Right);
+
+  // Get current PA7 state
+  bool prevPA7 = port0.myDigitalPinState[Controller::Four];
+
+  // Update entire port state
+  port0.update();
+  port1.update();
+  myConsole.switches().update();
+
+  // Get new PA7 state
+  bool currPA7 = port0.myDigitalPinState[Controller::Four];
+
+  // PA7 Flag is set on active transition in appropriate direction
+  if((!myEdgeDetectPositive && prevPA7 && !currPA7) ||
+     (myEdgeDetectPositive && !prevPA7 && currPA7))
+    myInterruptFlag |= PA7Bit;
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void M6532::install(System& system)
 {
@@ -181,7 +207,10 @@ uInt8 M6532::peek(uInt16 addr)
         myInterruptFlag |= TimerBit;
         myTimerFlagValid = true;
       }
-      return myInterruptFlag;
+      // PA7 Flag is always cleared after accessing TIMINT
+      uInt8 result = myInterruptFlag;
+      myInterruptFlag &= ~PA7Bit;
+      return result;
     }
 
     default:
@@ -208,10 +237,17 @@ bool M6532::poke(uInt16 addr, uInt8 value)
   }
 
   // A2 distinguishes I/O registers from the timer
+  // A2 = 1 is write to timer
+  // A2 = 0 is write to I/O
   if((addr & 0x04) != 0)
   {
-    if((addr & 0x10) != 0)  // TIMxT (x = 1, 8, 64, 1024)
-      setTimerRegister(value, addr & 0x03);
+    // A4 = 1 is write to TIMxT (x = 1, 8, 64, 1024)
+    // A4 = 0 is write to edge detect control
+    if((addr & 0x10) != 0)
+      setTimerRegister(value, addr & 0x03);  // A1A0 determines interval
+    else {
+      myEdgeDetectPositive = addr & 0x01;    // A0 determines direction
+cerr << "myEdgeDetectPositive: " << myEdgeDetectPositive << endl; }
   }
   else
   {
@@ -303,7 +339,6 @@ bool M6532::save(Serializer& out) const
   {
     out.putString(name());
 
-    // Output the RAM
     out.putByteArray(myRAM, 128);
 
     out.putInt(myTimer);
@@ -314,8 +349,10 @@ bool M6532::save(Serializer& out) const
     out.putByte(myDDRB);
     out.putByte(myOutA);
     out.putByte(myOutB);
+
     out.putByte(myInterruptFlag);
     out.putBool(myTimerFlagValid);
+    out.putBool(myEdgeDetectPositive);
     out.putByteArray(myOutTimer, 4);
   }
   catch(...)
@@ -335,7 +372,6 @@ bool M6532::load(Serializer& in)
     if(in.getString() != name())
       return false;
 
-    // Input the RAM
     in.getByteArray(myRAM, 128);
 
     myTimer = in.getInt();
@@ -346,8 +382,10 @@ bool M6532::load(Serializer& in)
     myDDRB = in.getByte();
     myOutA = in.getByte();
     myOutB = in.getByte();
+
     myInterruptFlag = in.getByte();
     myTimerFlagValid = in.getBool();
+    myEdgeDetectPositive = in.getBool();
     in.getByteArray(myOutTimer, 4);
   }
   catch(...)
diff --git a/src/emucore/M6532.hxx b/src/emucore/M6532.hxx
index cb98ea1d0..0f4bc865e 100644
--- a/src/emucore/M6532.hxx
+++ b/src/emucore/M6532.hxx
@@ -30,16 +30,13 @@ class Settings;
 
 /**
   This class models the M6532 RAM-I/O-Timer (aka RIOT) chip in the 2600
-  console.  Note that only the functionality used by the console is
-  emulated here; several aspects of the chip are completely ignored:
+  console.  Note that since the M6507 CPU doesn't contain an interrupt line,
+  the following functionality relating to the RIOT IRQ line is not emulated:
 
-    - Pin 25 (IRQ) is not connected at all, therefore all related
-      items are ignored (A3 determining IRQ enable/disable, etc).
+    - A3 to enable/disable interrupt from timer to IRQ
+    - A1 to enable/disable interrupt from PA7 to IRQ
 
-    - D6 of the Interrupt Flag is ignored, including PA7 interrupt flag (A1)
-      and negative/positive edge-detection (A0)
-
-  @author  Bradford W. Mott
+  @author  Bradford W. Mott and Stephen Anthony
   @version $Id$
 */
 class M6532 : public Device
@@ -77,6 +74,11 @@ class M6532 : public Device
     */
     void systemCyclesReset();
 
+    /**
+      Update the entire digital and analog pin state of ports A and B.
+    */
+    void update();
+
     /**
       Install 6532 in the specified system.  Invoked by the system
       when the 6532 is attached to it.
@@ -189,6 +191,10 @@ class M6532 : public Device
     // If it isn't valid, it will be updated as required
     bool myTimerFlagValid;
 
+    // Used to determine whether an active transition on PA7 has occurred
+    // True is positive edge-detect, false is negative edge-detect
+    bool myEdgeDetectPositive;
+
     // Last value written to the timer registers
     uInt8 myOutTimer[4];
 
diff --git a/src/emucore/StateManager.cxx b/src/emucore/StateManager.cxx
index 405cc1bd6..a8e8df579 100644
--- a/src/emucore/StateManager.cxx
+++ b/src/emucore/StateManager.cxx
@@ -30,7 +30,7 @@
 
 #include "StateManager.hxx"
 
-#define STATE_HEADER "03070102state"
+#define STATE_HEADER "03070103state"
 #define MOVIE_HEADER "03030000movie"
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -