X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=cpu%2Fmusashi%2Fm68k_in.c;h=d1756a53d491af71124be284461ee1b712232629;hb=c6e1e9779a5652b58ae638e40f4b01ccb223b0d0;hp=5fa68a9d66c1c8798e217d076069c9ff5c936b74;hpb=cc68a136aa179a5f32fe40208371eb9c2b0aadae;p=picodrive.git

diff --git a/cpu/musashi/m68k_in.c b/cpu/musashi/m68k_in.c
index 5fa68a9..d1756a5 100644
--- a/cpu/musashi/m68k_in.c
+++ b/cpu/musashi/m68k_in.c
@@ -8,10 +8,10 @@ must fix:
 /* ======================================================================== */
 /*
  *                                  MUSASHI
- *                                Version 3.3
+ *                                Version 3.31
  *
  * A portable Motorola M680x0 processor emulation engine.
- * Copyright 1998-2001 Karl Stenerud.  All rights reserved.
+ * Copyright 1998-2007 Karl Stenerud.  All rights reserved.
  *
  * This code may be freely used for non-commercial purposes as long as this
  * copyright notice remains unaltered in the source code and any binary files
@@ -259,6 +259,8 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 M68KMAKE_OPCODE_HANDLER_HEADER
 
 #include "m68kcpu.h"
+extern void m68040_fpu_op0(void);
+extern void m68040_fpu_op1(void);
 
 /* ======================================================================== */
 /* ========================= INSTRUCTION HANDLERS ========================= */
@@ -354,6 +356,8 @@ name    size  proc   ea   bit pattern       A+-DXWLdxI  0 1 2 4  000 010 020 040
 M68KMAKE_TABLE_START
 1010       0  .     .     1010............  ..........  U U U U   4   4   4   4
 1111       0  .     .     1111............  ..........  U U U U   4   4   4   4
+040fpu0   32  .     .     11110010........  ..........  . . . U   .   .   .   0
+040fpu1   32  .     .     11110011........  ..........  . . . U   .   .   .   0
 abcd       8  rr    .     1100...100000...  ..........  U U U U   6   6   4   4
 abcd       8  mm    ax7   1100111100001...  ..........  U U U U  18  18  16  16
 abcd       8  mm    ay7   1100...100001111  ..........  U U U U  18  18  16  16
@@ -492,9 +496,9 @@ chk2cmp2  32  .     pcdi  0000010011111010  ..........  . . U U   .   .  23  23
 chk2cmp2  32  .     pcix  0000010011111011  ..........  . . U U   .   .  23  23
 chk2cmp2  32  .     .     0000010011......  A..DXWL...  . . U U   .   .  18  18
 clr        8  .     d     0100001000000...  ..........  U U U U   4   4   2   2
-clr        8  .     .     0100001000......  A+-DXWL...  U U U U   6   4   4   4  notaz hack: changed 000 cycles 8 -> 6 like in starscream for Fatal Rewind
+clr        8  .     .     0100001000......  A+-DXWL...  U U U U   8   4   4   4
 clr       16  .     d     0100001001000...  ..........  U U U U   4   4   2   2
-clr       16  .     .     0100001001......  A+-DXWL...  U U U U   6   4   4   4  ditto
+clr       16  .     .     0100001001......  A+-DXWL...  U U U U   8   4   4   4
 clr       32  .     d     0100001010000...  ..........  U U U U   6   6   2   2
 clr       32  .     .     0100001010......  A+-DXWL...  U U U U  12   6   4   4
 cmp        8  .     d     1011...000000...  ..........  U U U U   4   4   2   2
@@ -885,19 +889,44 @@ M68KMAKE_OP(1111, 0, ., .)
 }
 
 
+M68KMAKE_OP(040fpu0, 32, ., .)
+{
+	if(CPU_TYPE_IS_040_PLUS(CPU_TYPE))
+	{
+		m68040_fpu_op0();
+		return;
+	}
+	m68ki_exception_1111();
+}
+
+
+M68KMAKE_OP(040fpu1, 32, ., .)
+{
+	if(CPU_TYPE_IS_040_PLUS(CPU_TYPE))
+	{
+		m68040_fpu_op1();
+		return;
+	}
+	m68ki_exception_1111();
+}
+
+
+
 M68KMAKE_OP(abcd, 8, rr, .)
 {
 	uint* r_dst = &DX;
 	uint src = DY;
 	uint dst = *r_dst;
 	uint res = LOW_NIBBLE(src) + LOW_NIBBLE(dst) + XFLAG_AS_1();
-
-	FLAG_V = ~res; /* Undefined V behavior */
+	uint corf = 0;
 
 	if(res > 9)
-		res += 6;
+		corf = 6;
 	res += HIGH_NIBBLE(src) + HIGH_NIBBLE(dst);
-	FLAG_X = FLAG_C = (res > 0x99) << 8;
+	FLAG_V = ~res; /* Undefined V behavior */
+
+	res += corf;
+	FLAG_X = FLAG_C = (res > 0x9f) << 8;
 	if(FLAG_C)
 		res -= 0xa0;
 
@@ -917,13 +946,15 @@ M68KMAKE_OP(abcd, 8, mm, ax7)
 	uint ea  = EA_A7_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(src) + LOW_NIBBLE(dst) + XFLAG_AS_1();
-
-	FLAG_V = ~res; /* Undefined V behavior */
+	uint corf = 0;
 
 	if(res > 9)
-		res += 6;
+		corf = 6;
 	res += HIGH_NIBBLE(src) + HIGH_NIBBLE(dst);
-	FLAG_X = FLAG_C = (res > 0x99) << 8;
+	FLAG_V = ~res; /* Undefined V behavior */
+
+	res += corf;
+	FLAG_X = FLAG_C = (res > 0x9f) << 8;
 	if(FLAG_C)
 		res -= 0xa0;
 
@@ -943,13 +974,15 @@ M68KMAKE_OP(abcd, 8, mm, ay7)
 	uint ea  = EA_AX_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(src) + LOW_NIBBLE(dst) + XFLAG_AS_1();
-
-	FLAG_V = ~res; /* Undefined V behavior */
+	uint corf = 0;
 
 	if(res > 9)
-		res += 6;
+		corf = 6;
 	res += HIGH_NIBBLE(src) + HIGH_NIBBLE(dst);
-	FLAG_X = FLAG_C = (res > 0x99) << 8;
+	FLAG_V = ~res; /* Undefined V behavior */
+
+	res += corf;
+	FLAG_X = FLAG_C = (res > 0x9f) << 8;
 	if(FLAG_C)
 		res -= 0xa0;
 
@@ -969,13 +1002,15 @@ M68KMAKE_OP(abcd, 8, mm, axy7)
 	uint ea  = EA_A7_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(src) + LOW_NIBBLE(dst) + XFLAG_AS_1();
-
-	FLAG_V = ~res; /* Undefined V behavior */
+	uint corf = 0;
 
 	if(res > 9)
-		res += 6;
+		corf = 6;
 	res += HIGH_NIBBLE(src) + HIGH_NIBBLE(dst);
-	FLAG_X = FLAG_C = (res > 0x99) << 8;
+	FLAG_V = ~res; /* Undefined V behavior */
+
+	res += corf;
+	FLAG_X = FLAG_C = (res > 0x9f) << 8;
 	if(FLAG_C)
 		res -= 0xa0;
 
@@ -995,13 +1030,15 @@ M68KMAKE_OP(abcd, 8, mm, .)
 	uint ea  = EA_AX_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(src) + LOW_NIBBLE(dst) + XFLAG_AS_1();
-
-	FLAG_V = ~res; /* Undefined V behavior */
+	uint corf = 0;
 
 	if(res > 9)
-		res += 6;
+		corf = 6;
 	res += HIGH_NIBBLE(src) + HIGH_NIBBLE(dst);
-	FLAG_X = FLAG_C = (res > 0x99) << 8;
+	FLAG_V = ~res; /* Undefined V behavior */
+
+	res += corf;
+	FLAG_X = FLAG_C = (res > 0x9f) << 8;
 	if(FLAG_C)
 		res -= 0xa0;
 
@@ -1210,8 +1247,9 @@ M68KMAKE_OP(adda, 16, ., a)
 M68KMAKE_OP(adda, 16, ., .)
 {
 	uint* r_dst = &AX;
+	uint src = MAKE_INT_16(M68KMAKE_GET_OPER_AY_16);
 
-	*r_dst = MASK_OUT_ABOVE_32(*r_dst + MAKE_INT_16(M68KMAKE_GET_OPER_AY_16));
+	*r_dst = MASK_OUT_ABOVE_32(*r_dst + src);
 }
 
 
@@ -1234,8 +1272,9 @@ M68KMAKE_OP(adda, 32, ., a)
 M68KMAKE_OP(adda, 32, ., .)
 {
 	uint* r_dst = &AX;
+	uint src = M68KMAKE_GET_OPER_AY_32; // notaz
 
-	*r_dst = MASK_OUT_ABOVE_32(*r_dst + M68KMAKE_GET_OPER_AY_32);
+	*r_dst = MASK_OUT_ABOVE_32(*r_dst + src);
 }
 
 
@@ -3100,8 +3139,8 @@ M68KMAKE_OP(bra, 8, ., .)
 {
 	m68ki_trace_t0();				   /* auto-disable (see m68kcpu.h) */
 	m68ki_branch_8(MASK_OUT_ABOVE_8(REG_IR));
-//	if(REG_PC == REG_PPC)
-//		USE_ALL_CYCLES();
+	if(REG_PC == REG_PPC)
+		USE_ALL_CYCLES();
 }
 
 
@@ -3111,8 +3150,8 @@ M68KMAKE_OP(bra, 16, ., .)
 	REG_PC -= 2;
 	m68ki_trace_t0();			   /* auto-disable (see m68kcpu.h) */
 	m68ki_branch_16(offset);
-//	if(REG_PC == REG_PPC)
-//		USE_ALL_CYCLES();
+	if(REG_PC == REG_PPC)
+		USE_ALL_CYCLES();
 }
 
 
@@ -3132,8 +3171,8 @@ M68KMAKE_OP(bra, 32, ., .)
 	{
 		m68ki_trace_t0();				   /* auto-disable (see m68kcpu.h) */
 		m68ki_branch_8(MASK_OUT_ABOVE_8(REG_IR));
-//		if(REG_PC == REG_PPC)
-//			USE_ALL_CYCLES();
+		if(REG_PC == REG_PPC)
+			USE_ALL_CYCLES();
 	}
 }
 
@@ -5258,7 +5297,7 @@ M68KMAKE_OP(jsr, 32, ., .)
 {
 	uint ea = M68KMAKE_GET_EA_AY_32;
 	m68ki_trace_t0();				   /* auto-disable (see m68kcpu.h) */
-	m68ki_push_32(MAKE_INT_24(REG_PC)); // notaz: Cyclone can't handle 32bit PC and I neet to debug it
+	m68ki_push_32(REG_PC);
 	m68ki_jump(ea);
 }
 
@@ -6426,7 +6465,8 @@ M68KMAKE_OP(move, 32, pd, d)
 	uint res = DY;
 	uint ea = EA_AX_PD_32();
 
-	m68ki_write_32(ea, res);
+	m68ki_write_16(ea+2, res & 0xFFFF );
+	m68ki_write_16(ea, (res >> 16) & 0xFFFF );
 
 	FLAG_N = NFLAG_32(res);
 	FLAG_Z = res;
@@ -6440,7 +6480,8 @@ M68KMAKE_OP(move, 32, pd, a)
 	uint res = AY;
 	uint ea = EA_AX_PD_32();
 
-	m68ki_write_32(ea, res);
+	m68ki_write_16(ea+2, res & 0xFFFF );
+	m68ki_write_16(ea, (res >> 16) & 0xFFFF );
 
 	FLAG_N = NFLAG_32(res);
 	FLAG_Z = res;
@@ -6454,7 +6495,8 @@ M68KMAKE_OP(move, 32, pd, .)
 	uint res = M68KMAKE_GET_OPER_AY_32;
 	uint ea = EA_AX_PD_32();
 
-	m68ki_write_32(ea, res);
+	m68ki_write_16(ea+2, res & 0xFFFF );
+	m68ki_write_16(ea, (res >> 16) & 0xFFFF );
 
 	FLAG_N = NFLAG_32(res);
 	FLAG_Z = res;
@@ -6921,7 +6963,15 @@ M68KMAKE_OP(movec, 32, rc, .)
 			case 0x002:			   /* CACR */
 				if(CPU_TYPE_IS_EC020_PLUS(CPU_TYPE))
 				{
-					REG_CACR = REG_DA[(word2 >> 12) & 15];
+					if (CPU_TYPE_IS_040_PLUS(CPU_TYPE))
+					{
+						REG_CACR = REG_DA[(word2 >> 12) & 15];
+					}
+					else
+					{
+						/* non 68040 can only set the lower 4 bits (C,CE,F,E) */
+						REG_CACR = REG_DA[(word2 >> 12) & 15] & 0x0f;
+					}
 					return;
 				}
 				m68ki_exception_illegal();
@@ -7093,7 +7143,12 @@ M68KMAKE_OP(movem, 32, re, pd)
 		if(register_list & (1 << i))
 		{
 			ea -= 4;
-			m68ki_write_32(ea, REG_DA[15-i]);
+#if 0
+			m68ki_write_32(ea, REG_DA[15-i] ); // notaz Cyclone hack
+#else
+			m68ki_write_16(ea+2, REG_DA[15-i] & 0xFFFF );
+			m68ki_write_16(ea, (REG_DA[15-i] >> 16) & 0xFFFF );
+#endif
 			count++;
 		}
 	AY = ea;
@@ -7749,19 +7804,19 @@ M68KMAKE_OP(mull, 32, ., .)
 M68KMAKE_OP(nbcd, 8, ., d)
 {
 	uint* r_dst = &DY;
-	uint dst = *r_dst;
-	uint res = MASK_OUT_ABOVE_8(0x9a - dst - XFLAG_AS_1());
+	uint dst = MASK_OUT_ABOVE_8(*r_dst);
+	uint res = -dst - XFLAG_AS_1();
 
-	if(res != 0x9a)
+	if(res != 0)
 	{
-		FLAG_V = ~res; /* Undefined V behavior */
+		FLAG_V = res; /* Undefined V behavior */
 
-		if((res & 0x0f) == 0xa)
-			res = (res & 0xf0) + 0x10;
+		if(((res|dst) & 0x0f) == 0)
+			res = (res & 0xf0) + 6;
 
-		res = MASK_OUT_ABOVE_8(res);
+		res = MASK_OUT_ABOVE_8(res + 0x9a);
 
-		FLAG_V &= res; /* Undefined V behavior part II */
+		FLAG_V &= ~res; /* Undefined V behavior part II */
 
 		*r_dst = MASK_OUT_BELOW_8(*r_dst) | res;
 
@@ -7783,18 +7838,18 @@ M68KMAKE_OP(nbcd, 8, ., .)
 {
 	uint ea = M68KMAKE_GET_EA_AY_8;
 	uint dst = m68ki_read_8(ea);
-	uint res = MASK_OUT_ABOVE_8(0x9a - dst - XFLAG_AS_1());
+	uint res = -dst - XFLAG_AS_1();
 
-	if(res != 0x9a)
+	if(res != 0)
 	{
-		FLAG_V = ~res; /* Undefined V behavior */
+		FLAG_V = res; /* Undefined V behavior */
 
-		if((res & 0x0f) == 0xa)
-			res = (res & 0xf0) + 0x10;
+		if(((res|dst) & 0x0f) == 0)
+			res = (res & 0xf0) + 6;
 
-		res = MASK_OUT_ABOVE_8(res);
+		res = MASK_OUT_ABOVE_8(res + 0x9a);
 
-		FLAG_V &= res; /* Undefined V behavior part II */
+		FLAG_V &= ~res; /* Undefined V behavior part II */
 
 		m68ki_write_8(ea, MASK_OUT_ABOVE_8(res));
 
@@ -8700,7 +8755,7 @@ M68KMAKE_OP(rol, 32, r, .)
 
 		*r_dst = res;
 
-		FLAG_C = (src >> (32 - shift)) << 8;
+		FLAG_C = (src >> ((32 - shift) & 0x1f)) << 8;
 		FLAG_N = NFLAG_32(res);
 		FLAG_Z = res;
 		FLAG_V = VFLAG_CLEAR;
@@ -9314,26 +9369,26 @@ M68KMAKE_OP(sbcd, 8, rr, .)
 	uint src = DY;
 	uint dst = *r_dst;
 	uint res = LOW_NIBBLE(dst) - LOW_NIBBLE(src) - XFLAG_AS_1();
+	uint corf = 0;
 
-//  FLAG_V = ~res; /* Undefined V behavior */
-	FLAG_V = VFLAG_CLEAR;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to assume cleared. */
-
-	if(res > 9)
-		res -= 6;
+	if(res > 0xf)
+		corf = 6;
 	res += HIGH_NIBBLE(dst) - HIGH_NIBBLE(src);
-	if(res > 0x99)
+	FLAG_V = res; /* Undefined V behavior */
+	if(res > 0xff)
 	{
 		res += 0xa0;
 		FLAG_X = FLAG_C = CFLAG_SET;
-		FLAG_N = NFLAG_SET;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to follow carry. */
 	}
+	else if(res < corf)
+		FLAG_X = FLAG_C = CFLAG_SET;
 	else
-		FLAG_N = FLAG_X = FLAG_C = 0;
+		FLAG_X = FLAG_C = 0;
 
-	res = MASK_OUT_ABOVE_8(res);
+	res = MASK_OUT_ABOVE_8(res - corf);
 
-//  FLAG_V &= res; /* Undefined V behavior part II */
-//  FLAG_N = NFLAG_8(res); /* Undefined N behavior */
+	FLAG_V &= ~res; /* Undefined V behavior part II */
+	FLAG_N = NFLAG_8(res); /* Undefined N behavior */
 	FLAG_Z |= res;
 
 	*r_dst = MASK_OUT_BELOW_8(*r_dst) | res;
@@ -9346,26 +9401,26 @@ M68KMAKE_OP(sbcd, 8, mm, ax7)
 	uint ea  = EA_A7_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(dst) - LOW_NIBBLE(src) - XFLAG_AS_1();
+	uint corf = 0;
 
-//  FLAG_V = ~res; /* Undefined V behavior */
-	FLAG_V = VFLAG_CLEAR;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to return zero. */
-
-	if(res > 9)
-		res -= 6;
+	if(res > 0xf)
+		corf = 6;
 	res += HIGH_NIBBLE(dst) - HIGH_NIBBLE(src);
-	if(res > 0x99)
+	FLAG_V = res; /* Undefined V behavior */
+	if(res > 0xff)
 	{
 		res += 0xa0;
 		FLAG_X = FLAG_C = CFLAG_SET;
-		FLAG_N = NFLAG_SET;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to follow carry. */
 	}
+	else if(res < corf)
+		FLAG_X = FLAG_C = CFLAG_SET;
 	else
-		FLAG_N = FLAG_X = FLAG_C = 0;
+		FLAG_X = FLAG_C = 0;
 
-	res = MASK_OUT_ABOVE_8(res);
+	res = MASK_OUT_ABOVE_8(res - corf);
 
-//  FLAG_V &= res; /* Undefined V behavior part II */
-//  FLAG_N = NFLAG_8(res); /* Undefined N behavior */
+	FLAG_V &= ~res; /* Undefined V behavior part II */
+	FLAG_N = NFLAG_8(res); /* Undefined N behavior */
 	FLAG_Z |= res;
 
 	m68ki_write_8(ea, res);
@@ -9378,26 +9433,26 @@ M68KMAKE_OP(sbcd, 8, mm, ay7)
 	uint ea  = EA_AX_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(dst) - LOW_NIBBLE(src) - XFLAG_AS_1();
+	uint corf = 0;
 
-//  FLAG_V = ~res; /* Undefined V behavior */
-	FLAG_V = VFLAG_CLEAR;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to return zero. */
-
-	if(res > 9)
-		res -= 6;
+	if(res > 0xf)
+		corf = 6;
 	res += HIGH_NIBBLE(dst) - HIGH_NIBBLE(src);
-	if(res > 0x99)
+	FLAG_V = res; /* Undefined V behavior */
+	if(res > 0xff)
 	{
 		res += 0xa0;
 		FLAG_X = FLAG_C = CFLAG_SET;
-		FLAG_N = NFLAG_SET;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to follow carry. */
 	}
+	else if(res < corf)
+		FLAG_X = FLAG_C = CFLAG_SET;
 	else
-		FLAG_N = FLAG_X = FLAG_C = 0;
+		FLAG_X = FLAG_C = 0;
 
-	res = MASK_OUT_ABOVE_8(res);
+	res = MASK_OUT_ABOVE_8(res - corf);
 
-//  FLAG_V &= res; /* Undefined V behavior part II */
-//  FLAG_N = NFLAG_8(res); /* Undefined N behavior */
+	FLAG_V &= ~res; /* Undefined V behavior part II */
+	FLAG_N = NFLAG_8(res); /* Undefined N behavior */
 	FLAG_Z |= res;
 
 	m68ki_write_8(ea, res);
@@ -9410,26 +9465,26 @@ M68KMAKE_OP(sbcd, 8, mm, axy7)
 	uint ea  = EA_A7_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(dst) - LOW_NIBBLE(src) - XFLAG_AS_1();
+	uint corf = 0;
 
-//  FLAG_V = ~res; /* Undefined V behavior */
-	FLAG_V = VFLAG_CLEAR;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to return zero. */
-
-	if(res > 9)
-		res -= 6;
+	if(res > 0xf)
+		corf = 6;
 	res += HIGH_NIBBLE(dst) - HIGH_NIBBLE(src);
-	if(res > 0x99)
+	FLAG_V = res; /* Undefined V behavior */
+	if(res > 0xff)
 	{
 		res += 0xa0;
 		FLAG_X = FLAG_C = CFLAG_SET;
-		FLAG_N = NFLAG_SET;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to follow carry. */
 	}
+	else if(res < corf)
+		FLAG_X = FLAG_C = CFLAG_SET;
 	else
-		FLAG_N = FLAG_X = FLAG_C = 0;
+		FLAG_X = FLAG_C = 0;
 
-	res = MASK_OUT_ABOVE_8(res);
+	res = MASK_OUT_ABOVE_8(res - corf);
 
-//  FLAG_V &= res; /* Undefined V behavior part II */
-//  FLAG_N = NFLAG_8(res); /* Undefined N behavior */
+	FLAG_V &= ~res; /* Undefined V behavior part II */
+	FLAG_N = NFLAG_8(res); /* Undefined N behavior */
 	FLAG_Z |= res;
 
 	m68ki_write_8(ea, res);
@@ -9442,26 +9497,26 @@ M68KMAKE_OP(sbcd, 8, mm, .)
 	uint ea  = EA_AX_PD_8();
 	uint dst = m68ki_read_8(ea);
 	uint res = LOW_NIBBLE(dst) - LOW_NIBBLE(src) - XFLAG_AS_1();
+	uint corf = 0;
 
-//  FLAG_V = ~res; /* Undefined V behavior */
-	FLAG_V = VFLAG_CLEAR;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to return zero. */
-
-	if(res > 9)
-		res -= 6;
+	if(res > 0xf)
+		corf = 6;
 	res += HIGH_NIBBLE(dst) - HIGH_NIBBLE(src);
-	if(res > 0x99)
+	FLAG_V = res; /* Undefined V behavior */
+	if(res > 0xff)
 	{
 		res += 0xa0;
 		FLAG_X = FLAG_C = CFLAG_SET;
-		FLAG_N = NFLAG_SET;	/* Undefined in Motorola's M68000PM/AD rev.1 and safer to follow carry. */
 	}
+	else if(res < corf)
+		FLAG_X = FLAG_C = CFLAG_SET;
 	else
-		FLAG_N = FLAG_X = FLAG_C = 0;
+		FLAG_X = FLAG_C = 0;
 
-	res = MASK_OUT_ABOVE_8(res);
+	res = MASK_OUT_ABOVE_8(res - corf);
 
-//  FLAG_V &= res; /* Undefined V behavior part II */
-//  FLAG_N = NFLAG_8(res); /* Undefined N behavior */
+	FLAG_V &= ~res; /* Undefined V behavior part II */
+	FLAG_N = NFLAG_8(res); /* Undefined N behavior */
 	FLAG_Z |= res;
 
 	m68ki_write_8(ea, res);
@@ -9720,8 +9775,9 @@ M68KMAKE_OP(suba, 16, ., a)
 M68KMAKE_OP(suba, 16, ., .)
 {
 	uint* r_dst = &AX;
+	uint src = MAKE_INT_16(M68KMAKE_GET_OPER_AY_16);
 
-	*r_dst = MASK_OUT_ABOVE_32(*r_dst - MAKE_INT_16(M68KMAKE_GET_OPER_AY_16));
+	*r_dst = MASK_OUT_ABOVE_32(*r_dst - src);
 }
 
 
@@ -9744,8 +9800,9 @@ M68KMAKE_OP(suba, 32, ., a)
 M68KMAKE_OP(suba, 32, ., .)
 {
 	uint* r_dst = &AX;
+	uint src = M68KMAKE_GET_OPER_AY_32; // notaz
 
-	*r_dst = MASK_OUT_ABOVE_32(*r_dst - M68KMAKE_GET_OPER_AY_32);
+	*r_dst = MASK_OUT_ABOVE_32(*r_dst - src);
 }
 
 
@@ -10149,12 +10206,20 @@ M68KMAKE_OP(tas, 8, ., .)
 {
 	uint ea = M68KMAKE_GET_EA_AY_8;
 	uint dst = m68ki_read_8(ea);
+	uint allow_writeback;
 
 	FLAG_Z = dst;
 	FLAG_N = NFLAG_8(dst);
 	FLAG_V = VFLAG_CLEAR;
 	FLAG_C = CFLAG_CLEAR;
-//	m68ki_write_8(ea, dst | 0x80); // notaz: genesis, but only to mem
+
+	/* The Genesis/Megadrive games Gargoyles and Ex-Mutants need the TAS writeback
+       disabled in order to function properly.  Some Amiga software may also rely
+       on this, but only when accessing specific addresses so additional functionality
+       will be needed. */
+	allow_writeback = m68ki_tas_callback();
+
+	if (allow_writeback==1) m68ki_write_8(ea, dst | 0x80);
 }