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/***************************************************************************************
* Genesis Plus
* Sega Graphic Board support
*
* Copyright (C) 2014 Eke-Eke (Genesis Plus GX)
*
* Redistribution and use of this code or any derivative works are permitted
* provided that the following conditions are met:
*
* - Redistributions may not be sold, nor may they be used in a commercial
* product or activity.
*
* - Redistributions that are modified from the original source must include the
* complete source code, including the source code for all components used by a
* binary built from the modified sources. However, as a special exception, the
* source code distributed need not include anything that is normally distributed
* (in either source or binary form) with the major components (compiler, kernel,
* and so on) of the operating system on which the executable runs, unless that
* component itself accompanies the executable.
*
* - Redistributions must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************************/
#include "shared.h"
static struct
{
uint8 State;
uint8 Counter;
uint8 Port;
} board;
void graphic_board_reset(int port)
{
input.analog[0][0] = 128;
input.analog[0][1] = 128;
board.State = 0x7f;
board.Counter = 0;
board.Port = port;
}
unsigned char graphic_board_read(void)
{
uint8 data;
if (board.State & 0x20)
{
return 0x60;
}
switch (board.Counter & 7)
{
case 0:
data = ~input.pad[board.Port];
break;
case 1:
data = 0x0f;
break;
case 2:
data = 0x0f;
break;
case 3:
data = input.analog[board.Port][0] >> 4;
break;
case 4:
data = input.analog[board.Port][0];
break;
case 5:
data = input.analog[board.Port][1] >> 4;
break;
case 6:
data = input.analog[board.Port][1];
break;
case 7:
data = 0x0f;
break;
}
return (board.State & ~0x1f) | (data & 0x0f);
}
void graphic_board_write(unsigned char data, unsigned char mask)
{
data = (board.State & ~mask) | (data & mask);
if ((data ^ board.State) & 0x20)
{
board.Counter = 0;
}
else if ((data ^ board.State) & 0x40)
{
board.Counter++;
}
board.State = data;
}
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