1 // license:BSD-3-Clause
2 // copyright-holders:Fabio Priuli
3 /**********************************************************************
4
5 Sega Master System "Graphic Board" emulation
6
7 I/O 3f write | this method
8 0x20 | 0x7f
9 0x00 | 0x3f
10 0x30 | 0xff
11
12 Typical sequence:
13 - 3f write 0x20
14 - read dc
15 - 3f write 0x00
16 - read dc
17 - 3f write 0x20
18 - read dc
19 - 3f write 0x30
20 Suspect from kind of counter that is reset by a 0x30 write to I/O port 0x3f.
21 Once reset reads from i/O port dc expect to see 0xE0.
22 And then any write with differing bits goes through several internal I/O ports
23 with the first port being the one with the buttons
24
25 In the reset/start state the lower four/five bits are 0.
26 Then a nibble is read containing the buttons (active low)
27 Then 2 nibbles are read to form a byte (first high nibble, then low nibble) indicating
28 whether the pen is on the graphic board, a value of FD, FE, or FF used for this. For
29 any other value the following 2 bytes are not read.
30 Then 2 nibbles are read to form a byte containing the absolute X coordinate.
31 Then 2 nibbles are read to form a byte containing the absolute Y coordiante.
32
33 **********************************************************************/
34
35 #include "emu.h"
36 #include "graphic.h"
37
38
39
40 //**************************************************************************
41 // DEVICE DEFINITIONS
42 //**************************************************************************
43
44 DEFINE_DEVICE_TYPE(SMS_GRAPHIC, sms_graphic_device, "sms_graphic", "Sega SMS Graphic Board")
45
46
INPUT_PORTS_START(sms_graphic)47 static INPUT_PORTS_START( sms_graphic )
48 PORT_START("BUTTONS")
49 PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 ) // MENU
50 PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON2 ) // DO
51 PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_BUTTON3 ) // PEN
52 PORT_BIT( 0xf8, IP_ACTIVE_LOW, IPT_UNUSED )
53
54 PORT_START("X")
55 PORT_BIT( 0xff, 0x00, IPT_LIGHTGUN_X) PORT_CROSSHAIR(X, 1.0, 0.0, 0) PORT_SENSITIVITY(50) PORT_KEYDELTA(15)
56
57 PORT_START("Y")
58 PORT_BIT( 0xff, 0x00, IPT_LIGHTGUN_Y) PORT_CROSSHAIR(Y, 1.0, 0.0, 0) PORT_SENSITIVITY(50) PORT_KEYDELTA(15)
59 INPUT_PORTS_END
60
61
62 //-------------------------------------------------
63 // input_ports - device-specific input ports
64 //-------------------------------------------------
65
66 ioport_constructor sms_graphic_device::device_input_ports() const
67 {
68 return INPUT_PORTS_NAME( sms_graphic );
69 }
70
71 //**************************************************************************
72 // LIVE DEVICE
73 //**************************************************************************
74
75 //-------------------------------------------------
76 // sms_graphic_device - constructor
77 //-------------------------------------------------
78
sms_graphic_device(const machine_config & mconfig,const char * tag,device_t * owner,uint32_t clock)79 sms_graphic_device::sms_graphic_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
80 : device_t(mconfig, SMS_GRAPHIC, tag, owner, clock)
81 , device_sms_control_port_interface(mconfig, *this)
82 , m_buttons(*this, "BUTTONS")
83 , m_x(*this, "X")
84 , m_y(*this, "Y")
85 , m_index(0)
86 , m_previous_write(0xff)
87 , m_pressure(0xfd)
88 {
89 }
90
91
92 //-------------------------------------------------
93 // device_start - device-specific startup
94 //-------------------------------------------------
95
device_start()96 void sms_graphic_device::device_start()
97 {
98 save_item(NAME(m_index));
99 save_item(NAME(m_previous_write));
100 }
101
102
103 //-------------------------------------------------
104 // sms_peripheral_r - joypad read
105 //-------------------------------------------------
106
peripheral_r()107 uint8_t sms_graphic_device::peripheral_r()
108 {
109 switch (m_index)
110 {
111 case 0: // Initial state / "I am a board"
112 // If any regular button is pressed raise/lower TL ?
113 // if ((m_buttons->read() & 0x07) != 0x07)
114 // return 0xf0;
115 return 0xd0;
116
117 case 1: // Read buttons (active low)
118 return m_buttons->read();
119
120 case 2: // Some thing only FD, FE, and FF cause the other values to be read
121 return m_pressure >> 4;
122
123 case 3:
124 return m_pressure & 0x0f;
125
126 case 4: // High nibble X?
127 return m_x->read() >> 4;
128
129 case 5: // Low nibble X?
130 return m_x->read() & 0x0f;
131
132 case 6: // High nibble Y?
133 return m_y->read() >> 4;
134
135 case 7: // Low Nibble Y?
136 return m_y->read() & 0x0f;
137 }
138
139 return 0xff;
140 }
141
peripheral_w(uint8_t data)142 void sms_graphic_device::peripheral_w(uint8_t data)
143 {
144 // Check for toggle on TH/TL
145 if ((data ^ m_previous_write) & 0xc0)
146 {
147 m_index++;
148 }
149
150 // If TR is high, restart
151 if (data & 0x80)
152 {
153 m_index = 0;
154 }
155
156 m_previous_write = data;
157 }
158