87 lines
1.9 KiB
C++
87 lines
1.9 KiB
C++
#include "stdafx.h"
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#include "GbTimer.h"
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#include "GbTypes.h"
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#include "GbMemoryManager.h"
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#include "GbApu.h"
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GbTimer::GbTimer(GbMemoryManager* memoryManager, GbApu* apu)
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{
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_apu = apu;
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_memoryManager = memoryManager;
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//Passes boot_div-dmgABCmgb
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//But that test depends on LCD power on timings, so may be wrong.
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_divider = 0x06;
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}
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GbTimer::~GbTimer()
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{
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}
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void GbTimer::Exec()
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{
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uint16_t newValue = _divider + 4;
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if(_timerEnabled && !(newValue & _timerDivider) && (_divider & _timerDivider)) {
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_counter++;
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if(_counter == 0) {
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_counter = _modulo;
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_memoryManager->RequestIrq(GbIrqSource::Timer);
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}
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}
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uint16_t frameSeqBit = _memoryManager->IsHighSpeed() ? 0x2000 : 0x1000;
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if(!(newValue & frameSeqBit) && (_divider & frameSeqBit)) {
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_apu->ClockFrameSequencer();
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}
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_divider = newValue;
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}
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uint8_t GbTimer::Read(uint16_t addr)
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{
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switch(addr) {
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case 0xFF04: return _divider >> 8;
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case 0xFF05: return _counter; //FF05 - TIMA - Timer counter (R/W)
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case 0xFF06: return _modulo; //FF06 - TMA - Timer Modulo (R/W)
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case 0xFF07: return _control | 0xF8; //FF07 - TAC - Timer Control (R/W)
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}
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return 0;
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}
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void GbTimer::Write(uint16_t addr, uint8_t value)
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{
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//TODO properly detect edges when setting new values to registers or disabling timer, etc.
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switch(addr) {
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case 0xFF04:
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_divider = 0;
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break;
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case 0xFF05:
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//FF05 - TIMA - Timer counter (R/W)
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_counter = value;
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break;
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case 0xFF06:
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//FF06 - TMA - Timer Modulo (R/W)
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_modulo = value;
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break;
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case 0xFF07:
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//FF07 - TAC - Timer Control (R/W)
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_control = value;
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_timerEnabled = (value & 0x04) != 0;
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switch(value & 0x03) {
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case 0: _timerDivider = 1 << 9; break;
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case 1: _timerDivider = 1 << 3; break;
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case 2: _timerDivider = 1 << 5; break;
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case 3: _timerDivider = 1 << 7; break;
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}
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break;
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}
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}
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void GbTimer::Serialize(Serializer& s)
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{
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s.Stream(_divider, _counter, _modulo, _control, _timerEnabled, _timerDivider);
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}
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