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pengo.cpp: better representation of schick's encryption by Haze. No functional change (nw)

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This commit is contained in:
Ivan Vangelista 2019-04-10 07:20:48 +02:00
parent 68a28d7fb6
commit b8c03be11b
1 changed files with 49 additions and 47 deletions
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96
src/mame/drivers/pengo.cpp
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@ -99,9 +99,13 @@ private:
DECLARE_WRITE_LINE_MEMBER(irq_mask_w);
DECLARE_WRITE_LINE_MEMBER(vblank_irq);
void decode_penta(int end, int nodecend);
void decode_schick_extra(int size, uint8_t* rom);
optional_shared_ptr<uint8_t> m_decrypted_opcodes;
optional_device<ls259_device> m_latch;
void decrypted_opcodes_map(address_map &map);
void schick_decrypted_opcodes_map(address_map &map);
void jrpacmbl_map(address_map &map);
void pengo_map(address_map &map);
void schick_map(address_map &map);
@ -204,6 +208,14 @@ void pengo_state::schick_map(address_map &map) // everything needs to be verifie
map(0x8800, 0x8fef).ram().share("mainram");
map(0x8ff0, 0x8fff).ram().share("spriteram");
map(0x9020, 0x902f).writeonly().share("spriteram2");
map(0xe000, 0xffff).rom();
}
void pengo_state::schick_decrypted_opcodes_map(address_map &map)
{
map(0x0000, 0xffff).rom().share("decrypted_opcodes");
map(0x8800, 0x8fef).ram().share("mainram");
map(0x8ff0, 0x8fff).ram().share("spriteram");
}
void pengo_state::schick_audio_map(address_map &map)
@ -530,7 +542,7 @@ void pengo_state::schick(machine_config &config) // all dividers unknown
/* basic machine hardware */
Z80(config, m_maincpu, MASTER_CLOCK/6);
m_maincpu->set_addrmap(AS_PROGRAM, &pengo_state::schick_map);
m_maincpu->set_addrmap(AS_OPCODES, &pengo_state::decrypted_opcodes_map);
m_maincpu->set_addrmap(AS_OPCODES, &pengo_state::schick_decrypted_opcodes_map);
z80_device &audiocpu(Z80(config, "audiocpu", MASTER_CLOCK/6));
audiocpu.set_addrmap(AS_PROGRAM, &pengo_state::schick_audio_map);
@ -835,7 +847,7 @@ ROM_END
void pengo_state::init_penta()
void pengo_state::decode_penta(int end, int nodecend)
{
/*
the values vary, but the translation mask is always laid out like this:
@ -880,7 +892,7 @@ void pengo_state::init_penta()
uint8_t *rom = memregion("maincpu")->base();
for (int A = 0x0000;A < 0x8000;A++)
for (int A = 0x0000;A < end;A++)
{
uint8_t src = rom[A];
@ -900,57 +912,47 @@ void pengo_state::init_penta()
i = ((A >> 4) & 1) + (((A >> 8) & 1) << 1) + (((A >> 12) & 1) << 2);
m_decrypted_opcodes[A] = src ^ opcode_xortable[i][j];
}
for (int A = end; A < nodecend; A++)
{
m_decrypted_opcodes[A] = rom[A];
}
}
void pengo_state::init_schick() // only the 0x0000-0x7fff range is correctly decrypted. 0x8000-0xdfff is 0xff, then 0xe000-0xffff seems to be differently encrypted.
void pengo_state::init_penta()
{
static const uint8_t data_xortable[4][8] =
{
{ 0xf1,0xd3,0x79,0x5b,0xd3,0xf1,0x5b,0x79 }, /* .......0.......0 */
{ 0xd9,0x5b,0xd3,0x51,0xd9,0x5b,0xd3,0x51 }, /* .......0.......1 */
{ 0xe1,0xc3,0x69,0x4b,0xc3,0xe1,0x4b,0x69 }, /* .......1.......0 */
{ 0xc9,0x4b,0xc3,0x41,0xc9,0x4b,0xc3,0x41 } /* .......1.......1 */
};
static const uint8_t opcode_xortable[8][8] =
{
{ 0x53,0x59,0x7b,0x71,0x71,0x7b,0x59,0x53 }, /* ...0...0...0.... */
{ 0xd9,0xd9,0x51,0x51,0xd9,0xd9,0x51,0x51 }, /* ...0...0...1.... */
{ 0xc9,0x4b,0xc3,0x41,0xe1,0x63,0xeb,0x69 }, /* ...0...1...0.... */
{ 0xc9,0x4b,0xc3,0x41,0xe1,0x63,0xeb,0x69 }, /* ...0...1...1.... */
{ 0x7b,0x59,0x7b,0x59,0xdb,0xf9,0xdb,0xf9 }, /* ...1...0...0.... */
{ 0x7b,0x59,0x7b,0x59,0xdb,0xf9,0xdb,0xf9 }, /* ...1...0...1.... */
{ 0xc9,0x4b,0xc3,0x41,0xe1,0x63,0xeb,0x69 }, /* ...1...1...0.... */
{ 0xc9,0x4b,0xc3,0x41,0xe1,0x63,0xeb,0x69 } /* ...1...1...1.... */
};
decode_penta(0x8000, 0x8000);
}
void pengo_state::decode_schick_extra(int size, uint8_t* rom)
{
// schick has an extra layer of encryption in addition to the penta encryption
for (int A = 0x0000; A < 0x10000; A++)
{
uint8_t srcdec = rom[A];
if (A & 0x100)
{
srcdec = bitswap<8>(srcdec^0x41, 7, 4, 5, 6, 3, 2, 1, 0);
}
else
{
srcdec = bitswap<8>(srcdec^0x51, 7, 6, 5, 0, 3, 2, 1, 4);
}
rom[A] = srcdec;
}
}
void pengo_state::init_schick()
{
uint8_t *rom = memregion("maincpu")->base();
for (int A = 0x0000;A < 0x10000;A++)
{
uint8_t src = rom[A];
decode_penta(0x8000, 0x10000);
/* pick the translation table from bits 0 and 8 of the address */
int i = (A & 1) + (((A >> 8) & 1) << 1);
/* pick the offset in the table from bits 1, 3 and 5 of the source data */
int j = ((src >> 1) & 1) + (((src >> 3) & 1) << 1) + (((src >> 5) & 1) << 2);
/* the bottom half of the translation table is the mirror image of the top */
if (src & 0x80) j = 7 - j;
/* decode the ROM data */
if (BIT(i, 1))
rom[A] = bitswap<8>(src ^ data_xortable[i][j], 7, 4, 5, 6, 3, 2, 1, 0);
else
rom[A] = bitswap<8>(src ^ data_xortable[i][j], 7, 6, 5, 0, 3, 2, 1, 4);
/* now decode the opcodes */
/* pick the translation table from bits 4, 8 and 12 of the address */
i = ((A >> 4) & 1) + (((A >> 8) & 1) << 1) + (((A >> 12) & 1) << 2);
if (BIT(i, 1))
m_decrypted_opcodes[A] = bitswap<8>(src ^ opcode_xortable[i][j], 7, 4, 5, 6, 3, 2, 1, 0);
else
m_decrypted_opcodes[A] = bitswap<8>(src ^ opcode_xortable[i][j], 7, 6, 5, 0, 3, 2, 1, 4);
}
decode_schick_extra(0x10000, rom);
decode_schick_extra(0x10000, m_decrypted_opcodes);
}