forked from libretro/snes9x
/
seta018.cpp
182 lines (153 loc) · 3.66 KB
/
seta018.cpp
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/*****************************************************************************\
Snes9x - Portable Super Nintendo Entertainment System (TM) emulator.
This file is licensed under the Snes9x License.
For further information, consult the LICENSE file in the root directory.
\*****************************************************************************/
#include "snes9x.h"
#include "memmap.h"
#include "seta.h"
static int line; // line counter
uint8 S9xGetST018 (uint32 Address)
{
uint8 t = 0;
uint16 address = (uint16) Address & 0xFFFF;
line++;
// these roles may be flipped
// op output
if (address == 0x3804)
{
if (ST018.out_count)
{
t = (uint8) ST018.output[ST018.out_index];
ST018.out_index++;
if (ST018.out_count == ST018.out_index)
ST018.out_count = 0;
}
else
t = 0x81;
}
// status register
else
if (address == 0x3800)
t = ST018.status;
#ifdef DEBUGGER
printf("ST018 R: %06X %02X\n", Address, t);
#endif
return (t);
}
void S9xSetST018 (uint8 Byte, uint32 Address)
{
static bool reset = false;
uint16 address = (uint16) Address & 0xFFFF;
#ifdef DEBUGGER
printf("ST018 W: %06X %02X\n", Address, Byte);
#endif
line++;
if (!reset)
{
// bootup values
ST018.waiting4command = true;
ST018.part_command = 0;
reset = true;
}
Memory.SRAM[address] = Byte;
// default status for now
ST018.status = 0x00;
// op data goes through this address
if (address == 0x3804)
{
// check for new commands: 3 bytes length
if (ST018.waiting4command && ST018.part_command == 2)
{
ST018.waiting4command = false;
ST018.in_index = 0;
ST018.out_index = 0;
ST018.part_command = 0; // 3-byte commands
ST018.pass = 0; // data streams into the chip
ST018.command <<= 8;
ST018.command |= Byte;
switch (ST018.command & 0xFFFFFF)
{
case 0x0100: ST018.in_count = 0; break;
case 0xFF00: ST018.in_count = 0; break;
default: ST018.waiting4command = true; break;
}
}
else
if (ST018.waiting4command)
{
// 3-byte commands
ST018.part_command++;
ST018.command <<= 8;
ST018.command |= Byte;
}
}
// extra parameters
else
if (address == 0x3802)
{
ST018.parameters[ST018.in_index] = Byte;
ST018.in_index++;
}
if (ST018.in_count == ST018.in_index)
{
// qctually execute the command
ST018.waiting4command = true;
ST018.in_index = 0;
ST018.out_index = 0;
switch (ST018.command)
{
// hardware check?
case 0x0100:
ST018.waiting4command = false;
ST018.pass++;
if (ST018.pass == 1)
{
ST018.in_count = 1;
ST018.out_count = 2;
// Overload's research
ST018.output[0x00] = 0x81;
ST018.output[0x01] = 0x81;
}
else
{
//ST018.in_count = 1;
ST018.out_count = 3;
// no reason to change this
//ST018.output[0x00] = 0x81;
//ST018.output[0x01] = 0x81;
ST018.output[0x02] = 0x81;
// done processing requests
if (ST018.pass == 3)
ST018.waiting4command = true;
}
break;
// unknown: feels like a security detection
// format identical to 0x0100
case 0xFF00:
ST018.waiting4command = false;
ST018.pass++;
if (ST018.pass == 1)
{
ST018.in_count = 1;
ST018.out_count = 2;
// Overload's research
ST018.output[0x00] = 0x81;
ST018.output[0x01] = 0x81;
}
else
{
//ST018.in_count = 1;
ST018.out_count = 3;
// no reason to change this
//ST018.output[0x00] = 0x81;
//ST018.output[0x01] = 0x81;
ST018.output[0x02] = 0x81;
// done processing requests
if (ST018.pass == 3)
ST018.waiting4command = true;
}
break;
}
}
}