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Diffstat (limited to 'src/mame/machine/deco102.cpp')
-rw-r--r--src/mame/machine/deco102.cpp85
1 files changed, 85 insertions, 0 deletions
diff --git a/src/mame/machine/deco102.cpp b/src/mame/machine/deco102.cpp
new file mode 100644
index 00000000000..3f0c79143f3
--- /dev/null
+++ b/src/mame/machine/deco102.cpp
@@ -0,0 +1,85 @@
+// license:BSD-3-Clause
+// copyright-holders:Nicola Salmoria
+/*
+
+ Data East Custom Chip 102 decryption
+ (encrypted 68000)
+
+ by Nicola Salmoria
+
+*/
+
+#include "emu.h"
+#include "cpu/m68000/m68000.h"
+#include "includes/decocrpt.h"
+
+static UINT16 decrypt(UINT16 data, int address, int select_xor)
+{
+ static const UINT16 xors[16] =
+ {
+ 0xb52c,0x2458,0x139a,0xc998,0xce8e,0x5144,0x0429,0xaad4,0xa331,0x3645,0x69a3,0xac64,0x1a53,0x5083,0x4dea,0xd237
+ };
+ static const UINT8 bitswaps[16][16] =
+ {
+ { 12,8,13,11,14,10,15,9, 3,2,1,0,4,5,6,7 }, { 10,11,14,12,15,13,8,9, 6,7,5,3,0,4,2,1 },
+ { 14,13,15,9,8,12,11,10, 7,4,1,5,6,0,3,2 }, { 15,14,8,9,10,11,13,12, 1,2,7,3,4,6,0,5 },
+ { 10,9,13,14,15,8,12,11, 5,2,1,0,3,4,7,6 }, { 8,9,15,14,10,11,13,12, 0,6,5,4,1,2,3,7 },
+ { 14,8,15,9,10,11,13,12, 4,5,3,0,2,7,6,1 }, { 13,11,12,10,15,9,14,8, 6,0,7,5,1,4,3,2 },
+ { 12,11,13,10,9,8,14,15, 0,2,4,6,7,5,3,1 }, { 15,13,9,8,10,11,12,14, 2,1,0,7,6,5,4,3 },
+ { 13,8,9,10,11,12,15,14, 6,0,1,2,3,7,4,5 }, { 12,11,10,8,9,13,14,15, 6,5,4,0,7,1,2,3 },
+ { 12,15,8,13,9,11,14,10, 6,5,4,3,2,1,0,7 }, { 11,12,13,14,15,8,9,10, 4,5,7,1,6,3,2,0 },
+ { 13,8,12,14,11,15,10,9, 7,6,5,4,3,2,1,0 }, { 15,14,13,12,11,10,9,8, 0,6,7,4,3,2,1,5 }
+ };
+ int j, xorval;
+ const UINT8 *bs;
+
+ // calculate bitswap to use
+ j = ((address ^ select_xor) & 0xf0) >> 4;
+ if (address & 0x20000) j ^= 4;
+ bs = bitswaps[j];
+
+ // calculate xor to use
+ j = (address ^ select_xor) & 0x0f;
+ if (address & 0x40000) j ^= 2; // boogwing
+ xorval = xors[j];
+
+ // decrypt
+ return xorval ^ BITSWAP16(data,
+ bs[0],bs[1],bs[2],bs[3],bs[4],bs[5],bs[6],bs[7],
+ bs[8],bs[9],bs[10],bs[11],bs[12],bs[13],bs[14],bs[15]);
+}
+
+void deco102_decrypt_cpu(UINT16 *rom, UINT16 *opcodes, int size, int address_xor, int data_select_xor, int opcode_select_xor)
+{
+ std::vector<UINT16> buf(size / 2);
+
+ memcpy(&buf[0], rom, size);
+
+ for (int i = 0; i < size / 2; i++)
+ {
+ int src;
+
+ // calculate address of encrypted word in ROM
+ src = i & 0xf0000;
+ if (i & 0x0001) src ^= 0xbe0b;
+ if (i & 0x0002) src ^= 0x5699;
+ if (i & 0x0004) src ^= 0x1322;
+ if (i & 0x0008) src ^= 0x0004;
+ if (i & 0x0010) src ^= 0x08a0;
+ if (i & 0x0020) src ^= 0x0089;
+ if (i & 0x0040) src ^= 0x0408;
+ if (i & 0x0080) src ^= 0x1212;
+ if (i & 0x0100) src ^= 0x08e0;
+ if (i & 0x0200) src ^= 0x5499;
+ if (i & 0x0400) src ^= 0x9a8b;
+ if (i & 0x0800) src ^= 0x1222;
+ if (i & 0x1000) src ^= 0x1200;
+ if (i & 0x2000) src ^= 0x0008;
+ if (i & 0x4000) src ^= 0x1210;
+ if (i & 0x8000) src ^= 0x00e0;
+ src ^= address_xor;
+
+ rom[i] = decrypt(buf[src], i, data_select_xor);
+ opcodes[i] = decrypt(buf[src], i, opcode_select_xor);
+ }
+}