6502/EightBit
1
0
Fork 0
mirror of https://github.com/MoleskiCoder/EightBit.git synced 2024-06-01 07:41:51 +00:00
Code Issues Projects Releases Wiki Activity

LR35902 Simplify timing mechanism (corrects some timing issues as well!)

Browse Source 
Signed-off-by: Adrian Conlon <adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2020-11-12 18:21:51 +00:00
parent b8a2db96f4
commit efed7dae23
4 changed files with 43 additions and 93 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
LR35902/inc/LR35902.h
View File

@ -48,38 +48,49 @@ namespace EightBit {
void handleRESET() final;
void handleINT() final;
void jr(int8_t offset) final {
IntelProcessor::jr(offset);
tick(5);
void memoryWrite() final {
tick();
IntelProcessor::memoryWrite();
}
int callConditional(const int condition) final {
if (IntelProcessor::callConditional(condition))
tick(3);
tick(3);
return condition;
uint8_t memoryRead() final {
tick();
return IntelProcessor::memoryRead();
}
void pushWord(register16_t value) final {
tick();
IntelProcessor::pushWord(value);
}
void jr(int8_t offset) final {
IntelProcessor::jr(offset);
tick();
}
int jumpConditional(const int condition) final {
IntelProcessor::jumpConditional(condition);
tick(3);
if (IntelProcessor::jumpConditional(condition))
tick();
return condition;
}
int returnConditional(const int condition) final {
if (IntelProcessor::returnConditional(condition))
tick(3);
tick(2);
IntelProcessor::returnConditional(condition);
tick();
return condition;
}
int jrConditional(const int condition) final {
if (IntelProcessor::jrConditional(condition))
if (!IntelProcessor::jrConditional(condition))
tick();
tick(2);
return condition;
}
void ret() final {
IntelProcessor::ret();
tick();
}
private:
Bus& m_bus;
@ -222,7 +233,7 @@ namespace EightBit {
[[nodiscard]] static uint8_t add(uint8_t& f, uint8_t operand, uint8_t value, int carry = 0);
[[nodiscard]] static uint8_t adc(uint8_t& f, uint8_t operand, uint8_t value);
[[nodiscard]] static uint8_t sbc(uint8_t& f, uint8_t operand, uint8_t value);
[[nodiscard]] static uint8_t andr(uint8_t& f, uint8_t operand, uint8_t value);
static uint8_t andr(uint8_t& f, uint8_t operand, uint8_t value);
[[nodiscard]] static uint8_t xorr(uint8_t& f, uint8_t operand, uint8_t value);
[[nodiscard]] static uint8_t orr(uint8_t& f, uint8_t operand, uint8_t value);
[[nodiscard]] static void compare(uint8_t& f, uint8_t operand, uint8_t value);

81
LR35902/src/LR35902.cpp
View File

@ -38,7 +38,6 @@ void EightBit::GameBoy::LR35902::handleINT() {
raiseHALT();
di();
restart(BUS().DATA());
tick(4);
}
void EightBit::GameBoy::LR35902::di() {
@ -83,11 +82,7 @@ bool EightBit::GameBoy::LR35902::convertCondition(const uint8_t f, int flag) {
}
void EightBit::GameBoy::LR35902::returnConditionalFlag(const uint8_t f, const int flag) {
if (convertCondition(f, flag)) {
tick(3);
ret();
}
tick(2);
returnConditional(convertCondition(f, flag));
}
void EightBit::GameBoy::LR35902::jrConditionalFlag(const uint8_t f, const int flag) {
@ -109,6 +104,8 @@ void EightBit::GameBoy::LR35902::reti() {
EightBit::register16_t EightBit::GameBoy::LR35902::add(uint8_t& f, const register16_t operand, const register16_t value) {
tick();
const int addition = operand.word + value.word;
const register16_t result = addition;
@ -238,8 +235,7 @@ void EightBit::GameBoy::LR35902::bit(uint8_t& f, const int n, const uint8_t oper
ASSUME(n >= 0);
ASSUME(n <= 7);
const auto carry = f & CF;
uint8_t discarded = operand;
andr(f, discarded, Chip::bit(n));
andr(f, operand, Chip::bit(n));
f = setBit(f, CF, carry);
}
@ -331,6 +327,7 @@ int EightBit::GameBoy::LR35902::step() {
} else if (UNLIKELY(lowered(INT()))) {
handleINT();
} else if (UNLIKELY(lowered(HALT()))) {
IntelProcessor::memoryRead(PC());
Processor::execute(0); // NOP
} else {
Processor::execute(fetchByte());
@ -397,29 +394,17 @@ void EightBit::GameBoy::LR35902::executeCB(const int x, const int y, const int z
default:
UNREACHABLE;
}
tick(2);
R(z, operand);
F() = adjustZero<LR35902>(F(), operand);
if (UNLIKELY(z == 6))
tick(2);
break;
} case 1: // BIT y, r[z]
bit(F(), y, R(z));
tick(2);
if (UNLIKELY(z == 6))
tick(2);
break;
case 2: // RES y, r[z]
R(z, res(y, R(z)));
tick(2);
if (UNLIKELY(z == 6))
tick(2);
break;
case 3: // SET y, r[z]
R(z, set(y, R(z)));
tick(2);
if (UNLIKELY(z == 6))
tick(2);
break;
default:
UNREACHABLE;
@ -433,20 +418,16 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
case 0: // Relative jumps and assorted ops
switch (y) {
case 0: // NOP
tick();
break;
case 1: // GB: LD (nn),SP
BUS().ADDRESS() = fetchWord();
setWord(SP());
tick(5);
break;
case 2: // GB: STOP
stop();
tick();
break;
case 3: // JR d
jr(fetchByte());
tick(4);
break;
case 4: // JR cc,d
case 5:
@ -462,11 +443,9 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (q) {
case 0: // LD rp,nn
RP(p) = fetchWord();
tick(3);
break;
case 1: // ADD HL,rp
HL() = add(F(), HL(), RP(p));
tick(2);
break;
default:
UNREACHABLE;
@ -478,19 +457,15 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (p) {
case 0: // LD (BC),A
IntelProcessor::memoryWrite(BC(), A());
tick(2);
break;
case 1: // LD (DE),A
IntelProcessor::memoryWrite(DE(), A());
tick(2);
break;
case 2: // GB: LDI (HL),A
IntelProcessor::memoryWrite(HL()++, A());
tick(2);
break;
case 3: // GB: LDD (HL),A
IntelProcessor::memoryWrite(HL()--, A());
tick(2);
break;
default:
UNREACHABLE;
@ -500,19 +475,15 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (p) {
case 0: // LD A,(BC)
A() = IntelProcessor::memoryRead(BC());
tick(2);
break;
case 1: // LD A,(DE)
A() = IntelProcessor::memoryRead(DE());
tick(2);
break;
case 2: // GB: LDI A,(HL)
A() = IntelProcessor::memoryRead(HL()++);
tick(2);
break;
case 3: // GB: LDD A,(HL)
A() = IntelProcessor::memoryRead(HL()--);
tick(2);
break;
default:
UNREACHABLE;
@ -533,25 +504,18 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
default:
UNREACHABLE;
}
tick(2);
tick();
break;
case 4: { // 8-bit INC
auto operand = R(y);
R(y, increment(F(), operand));
tick();
if (UNLIKELY(y == 6))
tick(2);
break;
} case 5: { // 8-bit DEC
auto operand = R(y);
R(y, decrement(F(), operand));
tick();
if (UNLIKELY(y == 6))
tick(2);
break;
} case 6: // 8-bit load immediate
R(y, fetchByte()); // LD r,n
tick(2);
break;
case 7: // Assorted operations on accumulator/flags
switch (y) {
@ -582,7 +546,6 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
default:
UNREACHABLE;
}
tick();
break;
default:
UNREACHABLE;
@ -593,10 +556,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
lowerHALT();
} else {
R(y, R(z));
if (UNLIKELY((y == 6) || (z == 6))) // M operations
tick();
}
tick();
break;
case 2: // Operate on accumulator and register/memory location
switch (y) {
@ -627,9 +587,6 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
default:
UNREACHABLE;
}
tick();
if (UNLIKELY(z == 6))
tick();
break;
case 3:
switch (z) {
@ -643,11 +600,11 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
break;
case 4: // GB: LD (FF00 + n),A
IntelProcessor::memoryWrite(IoRegisters::BASE + fetchByte(), A());
tick(3);
break;
case 5: { // GB: ADD SP,dd
const auto before = SP().word;
const int8_t value = fetchByte();
tick(2);
const auto result = before + value;
SP() = result;
const auto carried = before ^ value ^ (result & Mask16);
@ -655,15 +612,14 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
F() = setBit(F(), CF, carried & Bit8);
F() = setBit(F(), HC, carried & Bit4);
}
tick(4);
break;
case 6: // GB: LD A,(FF00 + n)
A() = IntelProcessor::memoryRead(IoRegisters::BASE + fetchByte());
tick(3);
break;
case 7: { // GB: LD HL,SP + dd
const auto before = SP().word;
const int8_t value = fetchByte();
tick();
const auto result = before + value;
HL() = result;
const auto carried = before ^ value ^ (result & Mask16);
@ -671,7 +627,6 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
F() = setBit(F(), CF, carried & Bit8);
F() = setBit(F(), HC, carried & Bit4);
}
tick(3);
break;
default:
UNREACHABLE;
@ -681,25 +636,21 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (q) {
case 0: // POP rp2[p]
RP2(p) = popWord();
tick(3);
break;
case 1:
switch (p) {
case 0: // RET
ret();
tick(4);
break;
case 1: // GB: RETI
reti();
tick(4);
break;
case 2: // JP HL
jump(HL());
tick();
break;
case 3: // LD SP,HL
SP() = HL();
tick(2);
tick();
break;
default:
UNREACHABLE;
@ -719,21 +670,17 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
break;
case 4: // GB: LD (FF00 + C),A
IntelProcessor::memoryWrite(IoRegisters::BASE + C(), A());
tick(2);
break;
case 5: // GB: LD (nn),A
BUS().ADDRESS() = MEMPTR() = fetchWord();
IntelProcessor::memoryWrite(A());
tick(4);
break;
case 6: // GB: LD A,(FF00 + C)
A() = IntelProcessor::memoryRead(IoRegisters::BASE + C());
tick(2);
break;
case 7: // GB: LD A,(nn)
BUS().ADDRESS() = MEMPTR() = fetchWord();
A() = busRead();
tick(4);
A() = memoryRead();
break;
default:
UNREACHABLE;
@ -743,7 +690,7 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (y) {
case 0: // JP nn
jump(MEMPTR() = fetchWord());
tick(4);
tick();
break;
case 1: // CB prefix
m_prefixCB = true;
@ -751,11 +698,9 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
break;
case 6: // DI
di();
tick();
break;
case 7: // EI
ei();
tick();
break;
}
break;
@ -766,13 +711,11 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
switch (q) {
case 0: // PUSH rp2[p]
pushWord(RP2(p));
tick(4);
break;
case 1:
switch (p) {
case 0: // CALL nn
call(MEMPTR() = fetchWord());
tick(6);
break;
}
break;
@ -809,11 +752,9 @@ void EightBit::GameBoy::LR35902::executeOther(const int x, const int y, const in
default:
UNREACHABLE;
}
tick(2);
break;
case 7: // Restart: RST y * 8
restart(y << 3);
tick(4);
break;
default:
UNREACHABLE;

7
inc/IntelProcessor.h
View File

@ -132,7 +132,7 @@ namespace EightBit {
//
void restart(const uint8_t address) {
virtual void restart(const uint8_t address) {
call(MEMPTR() = { address, 0 });
}
@ -169,7 +169,10 @@ namespace EightBit {
return condition;
}
void ret() final;
void ret() override {
Processor::ret();
MEMPTR() = PC();
}
private:
std::array<opcode_decoded_t, 0x100> m_decodedOpcodes;

5
src/IntelProcessor.cpp
View File

@ -40,8 +40,3 @@ void EightBit::IntelProcessor::setWord(const register16_t value) {
LittleEndianProcessor::setWord(value);
MEMPTR() = BUS().ADDRESS();
}
void EightBit::IntelProcessor::ret() {
Processor::ret();
MEMPTR() = PC();
}