// license:BSD-3-Clause // copyright-holders:Fabio Priuli /********************************************************************** Sega Master System "Graphic Board" emulation I/O 3f write | this method 0x20 | 0x7f 0x00 | 0x3f 0x30 | 0xff Typical sequence: - 3f write 0x20 - read dc - 3f write 0x00 - read dc - 3f write 0x20 - read dc - 3f write 0x30 Suspect from kind of counter that is reset by a 0x30 write to I/O port 0x3f. Once reset reads from i/O port dc expect to see 0xE0. And then any write with differing bits goes through several internal I/O ports with the first port being the one with the buttons In the reset/start state the lower four/five bits are 0. Then a nibble is read containing the buttons (active low) Then 2 nibbles are read to form a byte (first high nibble, then low nibble) indicating whether the pen is on the graphic board, a value of FD, FE, or FF used for this. For any other value the following 2 bytes are not read. Then 2 nibbles are read to form a byte containing the absolute X coordinate. Then 2 nibbles are read to form a byte containing the absolute Y coordiante. **********************************************************************/ #include "emu.h" #include "graphic.h" //************************************************************************** // DEVICE DEFINITIONS //************************************************************************** DEFINE_DEVICE_TYPE(SMS_GRAPHIC, sms_graphic_device, "sms_graphic", "Sega SMS Graphic Board") static INPUT_PORTS_START( sms_graphic ) PORT_START("BUTTONS") PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_BUTTON1 ) // MENU PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_BUTTON2 ) // DO PORT_BIT( 0x04, IP_ACTIVE_LOW, IPT_BUTTON3 ) // PEN PORT_BIT( 0xf8, IP_ACTIVE_LOW, IPT_UNUSED ) PORT_START("X") PORT_BIT( 0xff, 0x00, IPT_LIGHTGUN_X) PORT_CROSSHAIR(X, 1.0, 0.0, 0) PORT_SENSITIVITY(50) PORT_KEYDELTA(15) PORT_START("Y") PORT_BIT( 0xff, 0x00, IPT_LIGHTGUN_Y) PORT_CROSSHAIR(Y, 1.0, 0.0, 0) PORT_SENSITIVITY(50) PORT_KEYDELTA(15) INPUT_PORTS_END //------------------------------------------------- // input_ports - device-specific input ports //------------------------------------------------- ioport_constructor sms_graphic_device::device_input_ports() const { return INPUT_PORTS_NAME( sms_graphic ); } //************************************************************************** // LIVE DEVICE //************************************************************************** //------------------------------------------------- // sms_graphic_device - constructor //------------------------------------------------- sms_graphic_device::sms_graphic_device(const machine_config &mconfig, const char *tag, device_t *owner, const XTAL &clock) : device_t(mconfig, SMS_GRAPHIC, tag, owner, clock) , device_sms_control_port_interface(mconfig, *this) , m_buttons(*this, "BUTTONS") , m_x(*this, "X") , m_y(*this, "Y") , m_index(0) , m_previous_write(0xff) , m_pressure(0xfd) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void sms_graphic_device::device_start() { save_item(NAME(m_index)); save_item(NAME(m_previous_write)); } //------------------------------------------------- // sms_peripheral_r - joypad read //------------------------------------------------- uint8_t sms_graphic_device::peripheral_r() { switch (m_index) { case 0: // Initial state / "I am a board" // If any regular button is pressed raise/lower TL ? // if ((m_buttons->read() & 0x07) != 0x07) // return 0xf0; return 0xd0; case 1: // Read buttons (active low) return m_buttons->read(); case 2: // Some thing only FD, FE, and FF cause the other values to be read return m_pressure >> 4; case 3: return m_pressure & 0x0f; case 4: // High nibble X? return m_x->read() >> 4; case 5: // Low nibble X? return m_x->read() & 0x0f; case 6: // High nibble Y? return m_y->read() >> 4; case 7: // Low Nibble Y? return m_y->read() & 0x0f; } return 0xff; } void sms_graphic_device::peripheral_w(uint8_t data) { // Check for toggle on TH/TL if ((data ^ m_previous_write) & 0xc0) { m_index++; } // If TR is high, restart if (data & 0x80) { m_index = 0; } m_previous_write = data; }