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