183 lines
3.7 KiB
C++
183 lines
3.7 KiB
C++
/*****************************************************************************\
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Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
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This file is licensed under the Snes9x License.
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For further information, consult the LICENSE file in the root directory.
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\*****************************************************************************/
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#include "snes9x.h"
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#include "memmap.h"
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#include "seta.h"
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static int line; // line counter
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uint8 S9xGetST018 (uint32 Address)
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{
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uint8 t = 0;
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uint16 address = (uint16) Address & 0xFFFF;
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line++;
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// these roles may be flipped
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// op output
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if (address == 0x3804)
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{
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if (ST018.out_count)
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{
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t = (uint8) ST018.output[ST018.out_index];
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ST018.out_index++;
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if (ST018.out_count == ST018.out_index)
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ST018.out_count = 0;
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}
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else
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t = 0x81;
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}
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// status register
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else
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if (address == 0x3800)
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t = ST018.status;
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#ifdef DEBUGGER
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printf("ST018 R: %06X %02X\n", Address, t);
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#endif
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return (t);
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}
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void S9xSetST018 (uint8 Byte, uint32 Address)
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{
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static bool reset = false;
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uint16 address = (uint16) Address & 0xFFFF;
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#ifdef DEBUGGER
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printf("ST018 W: %06X %02X\n", Address, Byte);
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#endif
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line++;
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if (!reset)
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{
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// bootup values
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ST018.waiting4command = true;
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ST018.part_command = 0;
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reset = true;
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}
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Memory.SRAM[address] = Byte;
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// default status for now
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ST018.status = 0x00;
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// op data goes through this address
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if (address == 0x3804)
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{
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// check for new commands: 3 bytes length
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if (ST018.waiting4command && ST018.part_command == 2)
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{
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ST018.waiting4command = false;
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ST018.in_index = 0;
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ST018.out_index = 0;
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ST018.part_command = 0; // 3-byte commands
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ST018.pass = 0; // data streams into the chip
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ST018.command <<= 8;
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ST018.command |= Byte;
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switch (ST018.command & 0xFFFFFF)
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{
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case 0x0100: ST018.in_count = 0; break;
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case 0xFF00: ST018.in_count = 0; break;
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default: ST018.waiting4command = true; break;
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}
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}
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else
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if (ST018.waiting4command)
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{
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// 3-byte commands
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ST018.part_command++;
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ST018.command <<= 8;
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ST018.command |= Byte;
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}
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}
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// extra parameters
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else
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if (address == 0x3802)
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{
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ST018.parameters[ST018.in_index] = Byte;
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ST018.in_index++;
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}
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if (ST018.in_count == ST018.in_index)
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{
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// qctually execute the command
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ST018.waiting4command = true;
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ST018.in_index = 0;
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ST018.out_index = 0;
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switch (ST018.command)
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{
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// hardware check?
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case 0x0100:
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ST018.waiting4command = false;
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ST018.pass++;
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if (ST018.pass == 1)
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{
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ST018.in_count = 1;
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ST018.out_count = 2;
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// Overload's research
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ST018.output[0x00] = 0x81;
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ST018.output[0x01] = 0x81;
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}
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else
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{
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//ST018.in_count = 1;
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ST018.out_count = 3;
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// no reason to change this
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//ST018.output[0x00] = 0x81;
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//ST018.output[0x01] = 0x81;
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ST018.output[0x02] = 0x81;
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// done processing requests
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if (ST018.pass == 3)
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ST018.waiting4command = true;
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}
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break;
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// unknown: feels like a security detection
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// format identical to 0x0100
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case 0xFF00:
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ST018.waiting4command = false;
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ST018.pass++;
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if (ST018.pass == 1)
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{
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ST018.in_count = 1;
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ST018.out_count = 2;
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// Overload's research
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ST018.output[0x00] = 0x81;
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ST018.output[0x01] = 0x81;
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}
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else
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{
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//ST018.in_count = 1;
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ST018.out_count = 3;
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// no reason to change this
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//ST018.output[0x00] = 0x81;
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//ST018.output[0x01] = 0x81;
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ST018.output[0x02] = 0x81;
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// done processing requests
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if (ST018.pass == 3)
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ST018.waiting4command = true;
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}
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break;
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}
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}
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}
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