summaryrefslogtreecommitdiffstatshomepage
path: root/src/devices/bus/c64/dqbb.cpp
blob: e4d500575372506f34951798132a2421b2237064 (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
// license:BSD-3-Clause
// copyright-holders:Curt Coder
/**********************************************************************

    Brown Boxes Double Quick Brown Box emulation

**********************************************************************/

/*

    TODO:

    - 64/128 mode switch
    - dump of the initial NVRAM contents

*/

#include "emu.h"
#include "dqbb.h"



//**************************************************************************
//  DEVICE DEFINITIONS
//**************************************************************************

DEFINE_DEVICE_TYPE(C64_DQBB, c64_dqbb_cartridge_device, "c64_dqbb", "C64 Double Quick Brown Box cartridge")



//**************************************************************************
//  LIVE DEVICE
//**************************************************************************

//-------------------------------------------------
//  c64_dqbb_cartridge_device - constructor
//-------------------------------------------------

c64_dqbb_cartridge_device::c64_dqbb_cartridge_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock) :
	device_t(mconfig, C64_DQBB, tag, owner, clock),
	device_c64_expansion_card_interface(mconfig, *this),
	device_nvram_interface(mconfig, *this),
	m_cs(0),
	m_we(0)
{
}


//-------------------------------------------------
//  device_start - device-specific startup
//-------------------------------------------------

void c64_dqbb_cartridge_device::device_start()
{
	// allocate memory
	m_nvram = std::make_unique<uint8_t[]>(0x4000);
	save_pointer(NAME(m_nvram), 0x4000);

	// state saving
	save_item(NAME(m_cs));
	save_item(NAME(m_we));
}


//-------------------------------------------------
//  device_reset - device-specific reset
//-------------------------------------------------

void c64_dqbb_cartridge_device::device_reset()
{
	m_exrom = 0; // TODO 1 in 128 mode
	m_game = 1;
	m_cs = 0;
	m_we = 0;
}


void c64_dqbb_cartridge_device::nvram_default()
{
}


bool c64_dqbb_cartridge_device::nvram_read(util::read_stream &file)
{
	auto const [err, actual] = read(file, m_nvram.get(), 0x4000);
	return !err && (actual == 0x4000);
}


bool c64_dqbb_cartridge_device::nvram_write(util::write_stream &file)
{
	auto const [err, actual] = write(file, m_nvram.get(), 0x4000);
	return !err;
}


//-------------------------------------------------
//  c64_cd_r - cartridge data read
//-------------------------------------------------

uint8_t c64_dqbb_cartridge_device::c64_cd_r(offs_t offset, uint8_t data, int sphi2, int ba, int roml, int romh, int io1, int io2)
{
	if (!m_cs && (!roml || !romh))
	{
		data = m_nvram[offset & 0x3fff];
	}

	return data;
}


//-------------------------------------------------
//  c64_cd_w - cartridge data write
//-------------------------------------------------

void c64_dqbb_cartridge_device::c64_cd_w(offs_t offset, uint8_t data, int sphi2, int ba, int roml, int romh, int io1, int io2)
{
	if (!m_cs && m_we && (offset >= 0x8000 && offset < 0xc000))
	{
		m_nvram[offset & 0x3fff] = data;
	}
	else if (!io1)
	{
		/*

		    bit     description

		    0
		    1
		    2       GAME
		    3
		    4       WE
		    5
		    6       EXROM
		    7       _CS

		*/

		m_exrom = !BIT(data, 6);
		m_game = !BIT(data, 2);
		m_we = BIT(data, 4);
		m_cs = BIT(data, 7);
	}
}