[Core/MS] fixed disabled slot returned value

core/cart_hw/sms_cart.c

@@ -426,6 +426,7 @@ static unsigned char read_mapper_93c46(unsigned int address);
 static unsigned char read_mapper_terebi(unsigned int address);
 static unsigned char read_mapper_korea_8k(unsigned int address);
 static unsigned char read_mapper_default(unsigned int address);
+static unsigned char read_mapper_none(unsigned int address);
 
 void sms_cart_init(void)
 {
@@ -920,7 +921,7 @@ static void mapper_reset(void)
     }
 
     /* set default Z80 memory handlers */
-    z80_readmem = read_mapper_default;
+    z80_readmem = read_mapper_none;
     z80_writemem = write_mapper_none;
     return;
   }
@@ -1567,3 +1568,14 @@ static unsigned char read_mapper_default(unsigned int address)
 {
   return z80_readmap[address >> 10][address & 0x03FF];
 }
+
+static unsigned char read_mapper_none(unsigned int address)
+{
+  if (address >= 0xC000)
+  {
+    return z80_readmap[address >> 10][address & 0x03FF];
+  }
+
+  /* return last fetched z80 instruction / data */
+  return z80_last_fetch;
+}

core/z80/z80.c

@@ -210,6 +210,7 @@ UINT32 z80_cycle_ratio;
 #endif
 
 Z80_Regs Z80;
+UINT8 z80_last_fetch;
 
 unsigned char *z80_readmap[64];
 unsigned char *z80_writemap[64];
@@ -660,7 +661,8 @@ INLINE UINT8 ROP(void)
 {
   unsigned pc = PCD;
   PC++;
-  return cpu_readop(pc);
+  z80_last_fetch = cpu_readop(pc);
+  return z80_last_fetch;
 }
 
 /****************************************************************

core/z80/z80.h

@@ -50,6 +50,7 @@ typedef struct
 
 
 extern Z80_Regs Z80;
+extern UINT8 z80_last_fetch;
 
 #ifdef Z80_OVERCLOCK_SHIFT
 extern UINT32 z80_cycle_ratio;