summaryrefslogtreecommitdiffstatshomepage
path: root/src/mame/machine/k573fpga.cpp
blob: 3ea14abae9b869409722a27390b10f35e9ce3adf (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
// license:BSD-3-Clause
// copyright-holders:windyfairy
#include "emu.h"
#include "speaker.h"

#include "k573fpga.h"


k573fpga_device::k573fpga_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock) :
	device_t(mconfig, KONAMI_573_DIGITAL_FPGA, tag, owner, clock),
	use_ddrsbm_fpga(false)
{
}

void k573fpga_device::device_start()
{
}

void k573fpga_device::device_reset()
{
	mp3_cur_adr = 0;
	mp3_end_adr = 0;
	crypto_key1 = 0;
	crypto_key2 = 0;
	crypto_key3 = 0;
}

u16 k573fpga_device::get_mpeg_ctrl()
{
	if ((mpeg_ctrl_flag & 0xe000) == 0xe000) {
		// This has been tested with real hardware, but this flag is always held 0x1000 when the audio is being played
		return 0x1000;
	}

	return 0x0000;
}

void k573fpga_device::set_mpeg_ctrl(u16 data)
{
	logerror("FPGA MPEG control %c%c%c | %08x %08x\n",
				data & 0x8000 ? '#' : '.',
				data & 0x4000 ? '#' : '.',
				data & 0x2000 ? '#' : '.',
				mp3_cur_adr, mp3_end_adr);

	mpeg_ctrl_flag = data;
}

u16 k573fpga_device::decrypt_default(u16 v)
{
	u16 m = crypto_key1 ^ crypto_key2;

	v = bitswap<16>(
		v,
		15 - BIT(m, 0xF),
		14 + BIT(m, 0xF),
		13 - BIT(m, 0xE),
		12 + BIT(m, 0xE),
		11 - BIT(m, 0xB),
		10 + BIT(m, 0xB),
		9 - BIT(m, 0x9),
		8 + BIT(m, 0x9),
		7 - BIT(m, 0x8),
		6 + BIT(m, 0x8),
		5 - BIT(m, 0x5),
		4 + BIT(m, 0x5),
		3 - BIT(m, 0x3),
		2 + BIT(m, 0x3),
		1 - BIT(m, 0x2),
		0 + BIT(m, 0x2)
	);

	v ^= (BIT(m, 0xD) << 14) ^
		(BIT(m, 0xC) << 12) ^
		(BIT(m, 0xA) << 10) ^
		(BIT(m, 0x7) << 8) ^
		(BIT(m, 0x6) << 6) ^
		(BIT(m, 0x4) << 4) ^
		(BIT(m, 0x1) << 2) ^
		(BIT(m, 0x0) << 0);

	v ^= bitswap<16>(
		(u16)crypto_key3,
		7, 0, 6, 1,
		5, 2, 4, 3,
		3, 4, 2, 5,
		1, 6, 0, 7
	);

	crypto_key1 = (crypto_key1 & 0x8000) | ((crypto_key1 << 1) & 0x7FFE) | ((crypto_key1 >> 14) & 1);

	if(((crypto_key1 >> 15) ^ crypto_key1) & 1)
		crypto_key2 = (crypto_key2 << 1) | (crypto_key2 >> 15);

	crypto_key3++;

	return v;
}

u16 k573fpga_device::decrypt_ddrsbm(u16 data)
{
	u8 key[16] = {0};
	u16 key_state = bitswap<16>(
		crypto_key1,
		13, 11, 9, 7,
		5, 3, 1, 15,
		14, 12, 10, 8,
		6, 4, 2, 0
	);

	for(int i = 0; i < 8; i++) {
		key[i * 2] = key_state & 0xff;
		key[i * 2 + 1] = (key_state >> 8) & 0xff;
		key_state = ((key_state & 0x8080) >> 7) | ((key_state & 0x7f7f) << 1);
	}

	u16 output_word = 0;
	for(int cur_bit = 0; cur_bit < 8; cur_bit++) {
		int even_bit_shift = cur_bit * 2;
		int odd_bit_shift = cur_bit * 2 + 1;
		bool is_even_bit_set = data & (1 << even_bit_shift);
		bool is_odd_bit_set = data & (1 << odd_bit_shift);
		bool is_key_bit_set = key[crypto_key3 & 15] & (1 << cur_bit);
		bool is_scramble_bit_set = key[(crypto_key3 - 1) & 15] & (1 << cur_bit);

		if(is_scramble_bit_set)
			std::swap(is_even_bit_set, is_odd_bit_set);

		if(is_even_bit_set ^ is_key_bit_set)
			output_word |= 1 << even_bit_shift;

		if(is_odd_bit_set)
			output_word |= 1 << odd_bit_shift;
	}

	crypto_key3++;

	return output_word;
}

u16 k573fpga_device::get_decrypted()
{
	if(mp3_cur_adr >= mp3_end_adr || (mpeg_ctrl_flag & 0xe000) != 0xe000) {
		return 0;
	}

	u16 src = ram[mp3_cur_adr >> 1];
	u16 result = use_ddrsbm_fpga ? decrypt_ddrsbm(src) : decrypt_default(src);
	mp3_cur_adr += 2;

	return result;
}

DEFINE_DEVICE_TYPE(KONAMI_573_DIGITAL_FPGA, k573fpga_device, "k573fpga", "Konami 573 Digital I/O FPGA")