Reorganized random number generation code in each Cart class. There

was duplicate code in many Cart classes and in M6532 class, and since all
these classes are subclasses of Device, it made sense to move the
functionality there instead.

Carts 3E and E7 now return a random value when attempting to read from
the write port.  Still TODO is determine what happens to the value at
that address (is it randomized or zeroed?).  Thanks to Batari for
suggestions and sample code.

Fixed bug in E7 carts when entering the debugger; bankswitch was being
inadvertantly triggered which caused emulation to fail.

Overall, I need to figure out exactly what happens when reading from
the write port for all carts with extended RAM.  There are two things
to consider: what value is written to the address, and what value
is returned.


git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@1892 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba

src/emucore/Cart3E.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "TIA.hxx"
 #include "Cart3E.hxx"
@@ -50,9 +49,8 @@ Cartridge3E::~Cartridge3E()
 void Cartridge3E::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 32768; ++i)
-    myRam[i] = random.next();
+    myRam[i] = myRandGenerator.next();
 
   // We'll map bank 0 into the first segment upon reset
   bank(0);
@@ -97,13 +95,14 @@ void Cartridge3E::install(System& system)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt8 Cartridge3E::peek(uInt16 address)
 {
-  // TODO - determine what really happens when you read from the write port
   address &= 0x0FFF;
 
   if(address < 0x0800)
   {
     if(myCurrentBank < 256)
       return myImage[(address & 0x07FF) + (myCurrentBank << 11)];
+    else if(address < 0x400)  // Read from write port gives undefined values
+      return myRandGenerator.next();
     else
       return myRam[(address & 0x03FF) + ((myCurrentBank - 256) << 10)];
   }

src/emucore/Cart4A50.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "M6532.hxx"
 #include "TIA.hxx"
@@ -46,9 +45,8 @@ Cartridge4A50::~Cartridge4A50()
 void Cartridge4A50::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 32768; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   mySliceLow = mySliceMiddle = mySliceHigh = 0;
   myIsRomLow = myIsRomMiddle = myIsRomHigh = true;

src/emucore/CartAR.cxx

@@ -20,7 +20,6 @@
 #include <cstring>
 
 #include "M6502.hxx"
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartAR.hxx"
 
@@ -53,9 +52,8 @@ CartridgeAR::~CartridgeAR()
 void CartridgeAR::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 6 * 1024; ++i)
-    myImage[i] = random.next();
+    myImage[i] = myRandGenerator.next();
 
   // Initialize SC BIOS ROM
   initializeROM();
@@ -302,8 +300,7 @@ void CartridgeAR::initializeROM()
 
   // The accumulator should contain a random value after exiting the
   // SC BIOS code - a value placed in offset 281 will be stored in A
-  class Random random;
+  ourDummyROMCode[281] = myRandGenerator.next();
-  ourDummyROMCode[281] = random.next();
 
   // Initialize ROM with illegal 6502 opcode that causes a real 6502 to jam
   for(uInt32 i = 0; i < 2048; ++i)

src/emucore/CartCV.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartCV.hxx"
 
@@ -52,9 +51,8 @@ void CartridgeCV::reset()
     memcpy(myImage, myROM, 2048);
 
     // Initialize RAM with random values
-    class Random random;
     for(uInt32 i = 0; i < 1024; ++i)
-      myRAM[i] = random.next();
+      myRAM[i] = myRandGenerator.next();
   }
   else if(mySize == 4096)
   {

src/emucore/CartE7.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartE7.hxx"
 
@@ -46,9 +45,8 @@ CartridgeE7::~CartridgeE7()
 void CartridgeE7::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 2048; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Install some default banks for the RAM and first segment
   bankRAM(0);
@@ -109,7 +107,9 @@ uInt8 CartridgeE7::peek(uInt16 address)
   // NOTE: The following does not handle reading from RAM, however,
   // this function should never be called for RAM because of the
   // way page accessing has been setup
-  // TODO - determine what really happens when you read from the write port
+  if((bank() == 7) && (address < 0x400))
+    return myRandGenerator.next(); // Read from write port gives undefined values
+  else
     return myImage[(myCurrentSlice[address >> 11] << 11) + (address & 0x07FF)];
 }
 
@@ -136,6 +136,8 @@ void CartridgeE7::poke(uInt16 address, uInt8)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void CartridgeE7::bankRAM(uInt16 bank)
 { 
+  if(myBankLocked) return;
+
   // Remember what bank we're in
   myCurrentRAM = bank;
   uInt16 offset = bank << 8;

src/emucore/CartEFSC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartEFSC.hxx"
 
@@ -42,9 +41,8 @@ CartridgeEFSC::~CartridgeEFSC()
 void CartridgeEFSC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 128; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Upon reset we switch to bank 1
   bank(1);

src/emucore/CartF4SC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartF4SC.hxx"
 
@@ -42,9 +41,8 @@ CartridgeF4SC::~CartridgeF4SC()
 void CartridgeF4SC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 128; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Upon reset we switch to bank 0
   bank(0);

src/emucore/CartF6SC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartF6SC.hxx"
 
@@ -42,9 +41,8 @@ CartridgeF6SC::~CartridgeF6SC()
 void CartridgeF6SC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 128; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Upon reset we switch to bank 0
   bank(0);

src/emucore/CartF8SC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartF8SC.hxx"
 
@@ -42,9 +41,8 @@ CartridgeF8SC::~CartridgeF8SC()
 void CartridgeF8SC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 128; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Upon reset we switch to bank 1
   bank(1);

src/emucore/CartFASC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartFASC.hxx"
 
@@ -42,9 +41,8 @@ CartridgeFASC::~CartridgeFASC()
 void CartridgeFASC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 256; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 
   // Upon reset we switch to bank 2
   bank(2);
@@ -124,8 +122,12 @@ uInt8 CartridgeFASC::peek(uInt16 address)
   // Thanks to Kroko of AtariAge for this advice and code idea
   if(address < 0x0100)  // Write port is at 0xF000 - 0xF100 (256 bytes)
   {
-    if(myBankLocked) return 0;
+    if(!myBankLocked)
-    else return myRAM[address] = 0;
+    {
+      return myRAM[address] = 0;
+    }
+    else
+      return 0;
   }  
   else
   {

src/emucore/CartMC.cxx

@@ -19,7 +19,6 @@
 #include <cassert>
 #include <cstring>
 
-#include "Random.hxx"
 #include "System.hxx"
 #include "CartMC.hxx"
 
@@ -46,9 +45,8 @@ CartridgeMC::~CartridgeMC()
 void CartridgeMC::reset()
 {
   // Initialize RAM with random values
-  class Random random;
   for(uInt32 i = 0; i < 32768; ++i)
-    myRAM[i] = random.next();
+    myRAM[i] = myRandGenerator.next();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/emucore/M6532.cxx

@@ -20,7 +20,6 @@
 #include <iostream>
 
 #include "Console.hxx"
-#include "Random.hxx"
 #include "Switches.hxx"
 #include "System.hxx"
 
@@ -41,15 +40,13 @@ M6532::~M6532()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void M6532::reset()
 {
-  class Random random;
-
   // Randomize the 128 bytes of memory
   for(uInt32 t = 0; t < 128; ++t)
-    myRAM[t] = random.next();
+    myRAM[t] = myRandGenerator.next();
 
   // The timer absolutely cannot be initialized to zero; some games will
   // loop or hang (notably Solaris and H.E.R.O.)
-  myTimer = (0xff - (random.next() % 0xfe)) << 10;
+  myTimer = (0xff - (myRandGenerator.next() % 0xfe)) << 10;
   myIntervalShift = 10;
   myCyclesWhenTimerSet = 0;
   myInterruptEnabled = false;

src/emucore/Random.cxx

@@ -17,11 +17,18 @@
 //============================================================================
 
 #include <time.h>
+
 #include "OSystem.hxx"
 #include "Random.hxx"
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Random::Random()
+{
+  initSeed();
+}
+ 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void Random::initSeed()
 {
   if(ourSystem)
     myValue = ourSystem->getTicks();

src/emucore/Random.hxx

@@ -40,6 +40,12 @@ class Random
     Random();
     
   public:
+    /**
+      Re-initialize the random number generator with a new seed,
+      to generate a different set of random numbers.
+    */
+    void initSeed();
+
     /**
       Answer the next random number from the random number generator
 

src/emucore/m6502/src/Device.cxx

@@ -22,6 +22,7 @@
 Device::Device()
   : mySystem(0)
 {
+  myRandGenerator.initSeed();
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -35,3 +36,5 @@ void Device::systemCyclesReset()
   // By default I do nothing when my system resets its cycle counter
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+Random Device::myRandGenerator;

src/emucore/m6502/src/Device.hxx

@@ -21,6 +21,7 @@
 
 class System;
 
+#include "Random.hxx"
 #include "Serializable.hxx"
 #include "bspf.hxx"
 
@@ -107,6 +108,10 @@ class Device : public Serializable
   protected:
     /// Pointer to the system the device is installed in or the null pointer
     System* mySystem;
+
+    /// Many devices need a source of random numbers, usually for emulating
+    /// unknown/undefined behaviour
+    static class Random myRandGenerator;
 };
 
 #endif