.MD cartridge hardware (SRAM, etc) should not be reseted when emulating MCD hardware (fixes random crash when loading Mode 1 cartridge)

source/genesis.c

@@ -258,8 +258,21 @@ void gen_reset(int hard_reset)
   /* 8-bit / 16-bit modes */
   if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
   {
-    /* reset cartridge hardware & mapping */
+    if (system_hw == SYSTEM_MCD)
+    {
+      /* reset CD hardware */
+      scd_reset(1);
+
+      /* reset & halt SUB-CPU */
+      s68k.cycles = 0;
+      s68k_pulse_reset();
+      s68k_pulse_halt();
+    }
+    else
+    {
+      /* reset MD cartridge hardware */
       md_cart_reset(hard_reset);
+    }
 
     /* Z80 bus is released & Z80 is reseted */
     m68k.memory_map[0xa0].read8   = m68k_read_bus_8;
@@ -301,17 +314,6 @@ void gen_reset(int hard_reset)
       }
     }
 
-    if (system_hw == SYSTEM_MCD)
-    {
-      /* reset CD hardware */
-      scd_reset(1);
-
-      /* reset & halt SUB-CPU */
-      s68k.cycles = 0;
-      s68k_pulse_reset();
-      s68k_pulse_halt();
-    }
-
     /* reset MAIN-CPU */
     m68k_pulse_reset();
   }
@@ -375,6 +377,8 @@ void gen_tmss_w(unsigned int offset, unsigned int data)
 }
 
 void gen_bankswitch_w(unsigned int data)
+{
+  if (system_hw == SYSTEM_MD)
   {
     if (data & 1)
     {
@@ -387,12 +391,18 @@ void gen_bankswitch_w(unsigned int data)
       m68k.memory_map[0].base = boot_rom;
     }
   }
+}
 
 unsigned int gen_bankswitch_r(void)
+{
+  if (system_hw == SYSTEM_MD)
   {
     return (m68k.memory_map[0].base == cart.base);
   }
   
+  return 0xff;
+}
+
 
 /*-----------------------------------------------------------------------*/
 /* Z80 Bus controller chip functions (Genesis mode)                      */

source/loadrom.c

@@ -431,12 +431,6 @@ int load_bios(void)
 
           /* loaded BIOS region */
           system_bios = (system_bios & 0xf0) | (region_code >> 4);
-
-        }
-        else
-        {
-          /* CD BOOT ROM disabled (SYSTEM ERROR) */
-          memset(scd.bootrom, 0xff, sizeof(scd.bootrom));
         }
 
         return size;
@@ -543,13 +537,14 @@ int load_rom(char *filename)
   ggenie_shutdown();
   areplay_shutdown();
 
-  /* unload any existing disc */
   if (romtype == SYSTEM_MCD)
   {
+    /* unload CD image */
     cdd_unload();
   }
   else
   {
+    /* no CD image loaded */
     cdd.loaded = 0;
   }
 
@@ -590,11 +585,12 @@ int load_rom(char *filename)
     /* load file into ROM buffer */
     char extension[4];
     int size = load_archive(filename, cart.rom, sizeof(cart.rom), extension);
-    if (!size) return(0);
 
     /* mark CD BIOS as unloaded */
     system_bios &= ~0x10;
 
+    if (!size) return(0);
+
     /* convert lower case to upper case */
     *(uint32 *)(extension) &= 0xdfdfdfdf;
 
@@ -721,8 +717,11 @@ int load_rom(char *filename)
     /* boot from CD */
     scd.cartridge.boot = 0x00;
 
-    /* CD unloaded */
+    /* no CD image loaded */
     cdd.loaded = 0;
+
+    /* clear CD TOC */
+    cdd_unload();
   }
 
   /* special ROM cartridges that use CD hardware */
@@ -737,9 +736,12 @@ int load_rom(char *filename)
     /* load CD BOOT ROM */
     if (load_bios())
     {
-      /* CD unloaded */
+      /* no CD image loaded */
       cdd.loaded = 0;
 
+      /* clear CD TOC */
+      cdd_unload();
+
       /* boot from cartridge */
       scd.cartridge.boot = 0x40;
     }
@@ -747,6 +749,9 @@ int load_rom(char *filename)
     {
       /* assume Mega Drive hardware */
       system_hw = SYSTEM_MD;
+
+      /* copy back to cartridge ROM area */
+      memcpy(cart.rom, scd.cartridge.area, sizeof(scd.cartridge.area));
     }
   }