mirror of
https://github.com/libretro/vemulator-libretro.git
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139 lines
3.0 KiB
C++
139 lines
3.0 KiB
C++
/*
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VeMUlator - A Dreamcast Visual Memory Unit emulator for libretro
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Copyright (C) 2018 Mahmoud Jaoune
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "t0.h"
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VE_VMS_TIMER0::VE_VMS_TIMER0(VE_VMS_RAM *_ram, VE_VMS_INTERRUPTS *_intHandler, VE_VMS_CPU *_cpu, byte *_prescaler)
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{
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ram = _ram;
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intHandler = _intHandler;
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cpu = _cpu;
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prescaler = _prescaler;
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TRLStarted = 0;
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TRHStarted = 0;
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TRL_data = 0;
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TRH_data = 0;
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}
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VE_VMS_TIMER0::~VE_VMS_TIMER0()
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{
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}
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void VE_VMS_TIMER0::runTimer()
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{
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int TCNT_data = ram->readByte_RAW(T0CNT); //Timer control register
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bool TRLEnabled = (TCNT_data & 64) != 0;
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bool TRHEnabled = (TCNT_data & 128) != 0;
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bool TRLONGEnabled = (TCNT_data & 32) != 0;
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//Increase timers
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if(TRLEnabled)
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{
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if(TRLStarted++ == 0)
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TRL_data = ram->readByte_RAW(T0LR);
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else if(*prescaler == 1)
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TRL_data++;
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}
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else
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{
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TRL_data = ram->readByte_RAW(T0LR);
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TRLStarted = 0;
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}
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if(TRHEnabled)
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{
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if(TRHStarted++ == 0)
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TRH_data = ram->readByte_RAW(T0HR);
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else if(!TRLONGEnabled)
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{
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if(*prescaler == 1)
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TRH_data++;
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}
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}
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else
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{
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TRH_data = ram->readByte_RAW(T0HR);
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TRHStarted = 0;
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}
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//Overflow in TRL_data, 8-bit mode
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if(TRL_data > 255 && !TRLONGEnabled)
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{
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TCNT_data |= 2;
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if (TCNT_data & 1) intHandler->setINT2();
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//Stop timer
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//TCNT_data &= 0xBF;
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//Reload contents
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TRL_data = ram->readByte_RAW(T0LR);
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}
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//Overflow in TRL_data, 16-bit mode
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else if(TRL_data > 255 && TRLONGEnabled)
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{
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TRH_data++;
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if (TCNT_data & 1) intHandler->setINT2();
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//Reload contents
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TRL_data = ram->readByte_RAW(T0LR);
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//TRL_data = 0;
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}
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//Overflow in TRH_data, 8-bit mode
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if(TRH_data > 255 && !TRLONGEnabled)
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{
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TCNT_data |= 8;
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if (TCNT_data & 4) intHandler->setT0HOV();
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//Stop timer
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TCNT_data &= 0x7F; //Not forcefully stopping it causes a hang in Chao Adventure 1 when navigating through the menu
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//Reload contents
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TRH_data = ram->readByte_RAW(T0HR);
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}
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//Overflow in 16-bit mode
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else if(TRH_data > 255 && TRLONGEnabled)
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{
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//printf("T0 LONG overflow 16-bit\n");
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TCNT_data |= 2;
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TCNT_data |= 8;
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if (TCNT_data & 4) intHandler->setT0HOV();
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//Stop both timers
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//TCNT_data &= 0x3F;
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//Reload contents
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TRL_data = ram->readByte_RAW(T0LR);
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TRH_data = ram->readByte_RAW(T0HR);
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}
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ram->writeByte_RAW(T0L, TRL_data);
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ram->writeByte_RAW(T0H, TRH_data);
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ram->writeByte_RAW(T0CNT, TCNT_data);
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}
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