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Better DIV implementation. Incremented as a word and exposed as the high part in the DIV register.

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Signed-off-by: Adrian.Conlon <adrian.conlon@gmail.com>
This commit is contained in:
Adrian.Conlon
2017-09-01 13:17:20 +01:00
parent a2784ae02d
commit e42484d35c
2 changed files with 9 additions and 16 deletions
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9
LR35902/inc/Bus.h
View File

@@ -163,9 +163,9 @@ namespace EightBit {
return (peekRegister(TAC) & Processor::Bit2) == 0;
}
void incrementDIV() {
auto current = peekRegister(DIV);
pokeRegister(DIV, ++current);
void incrementDIV(int cycles) {
m_divCounter.word += cycles;
pokeRegister(DIV, m_divCounter.high);
}
void incrementTIMA() {
@@ -218,13 +218,12 @@ namespace EightBit {
int m_romBank;
int m_ramBank;
int m_divCounter;
register16_t m_divCounter;
int m_timerCounter;
int m_timerRate;
void Bus_WrittenByte(const AddressEventArgs& e);
void checkDiv(int cycles);
void checkTimer(int cycles);
void validateCartridgeType();

16
LR35902/src/Bus.cpp
View File

@@ -12,17 +12,19 @@ EightBit::Bus::Bus()
m_ramBankSwitching(false),
m_romBank(1),
m_ramBank(0),
m_divCounter(256),
m_timerCounter(0),
m_timerRate(0) {
m_bootRom.resize(0x100);
m_gameRom.resize(0x10000);
WrittenByte.connect(std::bind(&Bus::Bus_WrittenByte, this, std::placeholders::_1));
m_divCounter.word = 0xabcc;
}
void EightBit::Bus::reset() {
pokeRegister(NR52, 0xf1);
pokeRegister(LCDC, DisplayBackground | BackgroundCharacterDataSelection | LcdEnable);
m_divCounter.word = 0xabcc;
m_timerCounter = 0;
}
void EightBit::Bus::clear() {
@@ -109,7 +111,7 @@ void EightBit::Bus::Bus_WrittenByte(const AddressEventArgs& e) {
case BASE + DIV: // R/W
Memory::reference() = 0;
m_timerCounter = 0;
m_timerCounter = m_divCounter.word = 0;
break;
case BASE + TIMA: // R/W
case BASE + TMA: // R/W
@@ -164,18 +166,10 @@ void EightBit::Bus::Bus_WrittenByte(const AddressEventArgs& e) {
}
void EightBit::Bus::checkTimers(int cycles) {
checkDiv(cycles);
incrementDIV(cycles);
checkTimer(cycles);
}
void EightBit::Bus::checkDiv(int cycles) {
m_divCounter -= cycles;
if (m_divCounter <= 0) {
m_divCounter = 256;
incrementDIV();
}
}
void EightBit::Bus::checkTimer(int cycles) {
if (timerEnabled()) {
m_timerCounter -= cycles;