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CLK/Processors/65816/Implementation/65816Implementation.hpp

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//
// 65816Implementation.hpp
// Clock Signal
//
// Created by Thomas Harte on 27/09/2020.
// Copyright © 2020 Thomas Harte. All rights reserved.
//
template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler, uses_ready_line>::run_for(const Cycles cycles) {
#define perform_bus(address, value, operation) \
bus_address_ = (address) & 0xff'ffff; \
bus_value_ = value; \
bus_operation_ = operation
#define read(address, value) perform_bus(address, value, MOS6502Esque::Read)
#define write(address, value) perform_bus(address, value, MOS6502Esque::Write)
#define m_flag() registers_.mx_flags[0]
#define x_flag() registers_.mx_flags[1]
#define stack_address() ((registers_.s.full & registers_.e_masks[1]) | (0x0100 & registers_.e_masks[0]))
Cycles number_of_cycles = cycles + cycles_left_to_run_;
while(number_of_cycles > Cycles(0)) {
// Wait for ready to be inactive before proceeding.
while(uses_ready_line && ready_line_ && number_of_cycles > Cycles(0)) {
number_of_cycles -= bus_handler_.perform_bus_operation(BusOperation::Ready, static_cast<typename BusHandler::AddressType>(bus_address_), &bus_throwaway_);
}
// Process for as much time is left and/or until ready is signalled.
while((!uses_ready_line || !ready_line_) && number_of_cycles > Cycles(0)) {
const MicroOp operation = *next_op_;
++next_op_;
#ifndef NDEBUG
// As a sanity check.
bus_value_ = nullptr;
#endif
switch(operation) {
//
// Scheduling.
//
case OperationMoveToNextProgram: {
// The exception program will determine the appropriate way to respond
// based on the pending exception if one exists; otherwise just do a
// standard fetch-decode-execute.
if(selected_exceptions_) {
exception_is_interrupt_ = true;
// Do enough quick early decoding to spot a reset.
if(selected_exceptions_ & (Reset | PowerOn)) {
active_instruction_ = &instructions[size_t(OperationSlot::Reset)];
} else {
active_instruction_ = &instructions[size_t(OperationSlot::Exception)];
}
} else {
exception_is_interrupt_ = false;
active_instruction_ = &instructions[size_t(OperationSlot::FetchDecodeExecute)];
}
next_op_ = &micro_ops_[active_instruction_->program_offsets[0]];
instruction_buffer_.clear();
data_buffer_.clear();
last_operation_pc_ = registers_.pc;
last_operation_program_bank_ = uint8_t(registers_.program_bank >> 16);
memory_lock_ = false;
} continue;
case OperationDecode: {
active_instruction_ = &instructions[instruction_buffer_.value];
const auto size_flag = registers_.mx_flags[active_instruction_->size_field];
next_op_ = &micro_ops_[active_instruction_->program_offsets[size_flag]];
instruction_buffer_.clear();
} continue;
//
// PC fetches.
//
case CycleFetchOpcode:
perform_bus(registers_.pc | registers_.program_bank, instruction_buffer_.next_input(), MOS6502Esque::ReadOpcode);
++registers_.pc;
break;
case CycleFetchIncrementPC:
perform_bus(registers_.pc | registers_.program_bank, instruction_buffer_.next_input(), MOS6502Esque::ReadProgram);
++registers_.pc;
break;
case CycleFetchPC:
perform_bus(registers_.pc | registers_.program_bank, instruction_buffer_.next_input(), MOS6502Esque::ReadProgram);
break;
case CycleFetchPCThrowaway:
perform_bus(registers_.pc | registers_.program_bank, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
case CycleFetchPreviousPCThrowaway:
perform_bus(((registers_.pc - 1) & 0xffff) | registers_.program_bank, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
case CycleFetchPreviousThrowaway:
perform_bus(bus_address_, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
//
// Data fetches and stores.
//
#define increment_data_address() data_address_ = (data_address_ & ~data_address_increment_mask_) + ((data_address_ + 1) & data_address_increment_mask_)
#define decrement_data_address() data_address_ = (data_address_ & ~data_address_increment_mask_) + ((data_address_ - 1) & data_address_increment_mask_)
case CycleFetchData:
read(data_address_, data_buffer_.next_input());
break;
case CycleStoreOrFetchDataThrowaway:
if(registers_.emulation_flag) {
perform_bus(data_address_, data_buffer_.preview_output(), MOS6502Esque::InternalOperationWrite);
break;
}
[[fallthrough]];
case CycleFetchDataThrowaway:
perform_bus(data_address_, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
case CycleFetchIncorrectDataAddress:
perform_bus(incorrect_data_address_, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
case CycleFetchIncrementData:
read(data_address_, data_buffer_.next_input());
increment_data_address();
break;
case CycleFetchVector:
perform_bus(data_address_, data_buffer_.next_input(), MOS6502Esque::ReadVector);
break;
case CycleFetchIncrementVector:
perform_bus(data_address_, data_buffer_.next_input(), MOS6502Esque::ReadVector);
increment_data_address();
break;
case CycleStoreData:
write(data_address_, data_buffer_.next_output());
break;
case CycleStoreIncrementData:
write(data_address_, data_buffer_.next_output());
increment_data_address();
break;
case CycleStoreDecrementData:
write(data_address_, data_buffer_.next_output_descending());
decrement_data_address();
break;
case CycleFetchBlockX:
read(((instruction_buffer_.value & 0xff00) << 8) | registers_.x.full, data_buffer_.any_byte());
break;
case CycleFetchBlockY:
perform_bus(((instruction_buffer_.value & 0x00ff) << 16) | registers_.y.full, &bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
case CycleStoreBlockY:
write(((instruction_buffer_.value & 0x00ff) << 16) | registers_.y.full, data_buffer_.any_byte());
break;
#undef increment_data_address
#undef decrement_data_address
//
// Stack accesses.
//
#define stack_access(value, operation) \
bus_address_ = stack_address(); \
bus_value_ = value; \
bus_operation_ = operation;
case CyclePush:
stack_access(data_buffer_.next_output_descending(), MOS6502Esque::Write);
--registers_.s.full;
break;
case CyclePushNotEmulation:
bus_address_ = registers_.s.full;
bus_value_ = data_buffer_.next_output_descending();
bus_operation_ = MOS6502Esque::Write;
--registers_.s.full;
break;
case CyclePullIfNotEmulation:
if(registers_.emulation_flag) {
continue;
}
[[fallthrough]];
case CyclePull:
++registers_.s.full;
stack_access(data_buffer_.next_input(), MOS6502Esque::Read);
break;
case CyclePullNotEmulation:
++registers_.s.full;
bus_address_ = registers_.s.full;
bus_value_ = data_buffer_.next_input();
bus_operation_ = MOS6502Esque::Read;
break;
case CycleAccessStack:
stack_access(&bus_throwaway_, MOS6502Esque::InternalOperationRead);
break;
#undef stack_access
//
// Memory lock control.
//
case OperationSetMemoryLock:
memory_lock_ = true;
continue;
//
// STP and WAI.
//
case CycleRepeatingNone:
if(selected_exceptions_ & required_exceptions_) {
continue;
} else {
--next_op_;
perform_bus(0xffffff, &bus_throwaway_, (required_exceptions_ & IRQ) ? MOS6502Esque::Ready : MOS6502Esque::None);
}
break;
//
// Data movement.
//
case OperationCopyPCToData:
data_buffer_.size = 2;
data_buffer_.value = registers_.pc;
continue;
case OperationCopyInstructionToData:
data_buffer_ = instruction_buffer_;
continue;
case OperationCopyDataToInstruction:
instruction_buffer_ = data_buffer_;
data_buffer_.clear();
continue;
case OperationCopyAToData:
data_buffer_.value = registers_.a.full & registers_.m_masks[1];
data_buffer_.size = 2 - m_flag();
continue;
case OperationCopyDataToA:
registers_.a.full = (registers_.a.full & registers_.m_masks[0]) + (data_buffer_.value & registers_.m_masks[1]);
continue;
case OperationCopyPBRToData:
data_buffer_.size = 1;
data_buffer_.value = registers_.program_bank >> 16;
continue;
case OperationCopyDataToPC:
registers_.pc = uint16_t(data_buffer_.value);
continue;
case OperationClearDataBuffer:
data_buffer_.clear();
continue;
//
// Address construction.
//
case OperationConstructAbsolute:
data_address_ = instruction_buffer_.value + registers_.data_bank;
data_address_increment_mask_ = 0xff'ff'ff;
continue;
case OperationConstructAbsolute16:
data_address_ = instruction_buffer_.value;
data_address_increment_mask_ = 0x00'ff'ff;
continue;
case OperationConstructAbsoluteLong:
data_address_ = instruction_buffer_.value;
data_address_increment_mask_ = 0xff'ff'ff;
continue;
// Used for JMP and JSR (absolute, x).
case OperationConstructAbsoluteIndexedIndirect:
data_address_ = registers_.program_bank + ((instruction_buffer_.value + registers_.x.full) & 0xffff);
data_address_increment_mask_ = 0x00'ff'ff;
continue;
case OperationConstructAbsoluteLongX:
data_address_ = instruction_buffer_.value + registers_.x.full;
data_address_increment_mask_ = 0xff'ff'ff;
continue;
case OperationConstructAbsoluteXRead:
case OperationConstructAbsoluteX:
data_address_ = instruction_buffer_.value + registers_.x.full + registers_.data_bank;
incorrect_data_address_ = ((data_address_ & 0x00ff) | (instruction_buffer_.value & 0xff00)) + registers_.data_bank;
// "Add 1 cycle for indexing across page boundaries, or write, or X=0"
// (i.e. don't add 1 cycle if x = 1 and this is a read, and a page boundary wasn't crossed)
if(
operation == OperationConstructAbsoluteXRead &&
data_address_ == incorrect_data_address_ &&
registers_.mx_flags[1]) {
++next_op_;
}
data_address_increment_mask_ = 0xff'ff'ff;
continue;
case OperationConstructAbsoluteYRead:
case OperationConstructAbsoluteY:
data_address_ = instruction_buffer_.value + registers_.y.full + registers_.data_bank;
incorrect_data_address_ = (data_address_ & 0xff) + (instruction_buffer_.value & 0xff00) + registers_.data_bank;
// "Add 1 cycle for indexing across page boundaries, or write, or X=0"
// (i.e. don't add 1 cycle if x = 1 and this is a read, and a page boundary wasn't crossed)
if(
operation == OperationConstructAbsoluteYRead &&
data_address_ == incorrect_data_address_ &&
registers_.mx_flags[1]) {
++next_op_;
}
data_address_increment_mask_ = 0xff'ff'ff;
continue;
case OperationConstructDirect:
data_address_ = (registers_.direct + instruction_buffer_.value) & 0xffff;
data_address_increment_mask_ = 0x00'ff'ff;
if(!(registers_.direct&0xff)) {
// If the low byte is 0 and this is emulation mode, incrementing
// is restricted to the low byte.
data_address_increment_mask_ = registers_.e_masks[1];
++next_op_;
}
continue;
case OperationConstructDirectLong:
data_address_ = (registers_.direct + instruction_buffer_.value) & 0xffff;
data_address_increment_mask_ = 0x00'ff'ff;
if(!(registers_.direct&0xff)) {
++next_op_;
}
continue;
case OperationConstructDirectIndirect:
data_address_ = registers_.data_bank + data_buffer_.value;
data_address_increment_mask_ = 0xff'ff'ff;
data_buffer_.clear();
continue;
case OperationConstructDirectIndexedIndirect:
// Emulation mode plus DL = 0 is required for 6502-style functionality where
// only the low byte is the result of the indirect calculation.
if(!(registers_.direct&0xff)) {
data_address_ = (
((registers_.direct + registers_.x.full + instruction_buffer_.value) & registers_.e_masks[1]) +
(registers_.direct & registers_.e_masks[0])
) & 0xffff;
++next_op_;
} else {
data_address_ = (
registers_.direct + registers_.x.full + instruction_buffer_.value
) & 0xffff;
}
data_address_increment_mask_ = 0x00'ff'ff;
continue;
case OperationConstructDirectIndirectIndexedLong:
data_address_ = registers_.y.full + data_buffer_.value;
data_address_increment_mask_ = 0xff'ff'ff;
data_buffer_.clear();
continue;
case OperationConstructDirectIndirectLong:
data_address_ = data_buffer_.value;
data_address_increment_mask_ = 0xff'ff'ff;
data_buffer_.clear();
continue;
case OperationConstructDirectX:
// There are no direct, x instructions that access a two-byte value when
// in emulation mode, so this can assume native mode.
data_address_increment_mask_ = 0x00'ff'ff;
// If the low byte of the direct register is 0, use the current e mask
// potentially to keep the high byte of the direct register unmodified.
//
// Also skip the next program step, which would be a redundant fetch
// from the program counter.
//
// Otherwise: retain a 16-bit address.
data_address_ = instruction_buffer_.value + registers_.direct + registers_.x.full;
if(!(registers_.direct&0xff)) {
data_address_ =
(registers_.direct & registers_.e_masks[0]) |
(data_address_ & registers_.e_masks[1]);
++next_op_;
} else {
data_address_ &= 0xffff;
}
continue;
case OperationConstructDirectY:
// Cf. comments above in DirectX.
data_address_increment_mask_ = 0x00'ff'ff;
data_address_ = instruction_buffer_.value + registers_.direct + registers_.y.full;
if(!(registers_.direct&0xff)) {
data_address_ =
(registers_.direct & registers_.e_masks[0]) |
(data_address_ & registers_.e_masks[1]);
++next_op_;
} else {
data_address_ &= 0xffff;
}
continue;
case OperationConstructStackRelative:
data_address_ = (stack_address() + instruction_buffer_.value) & 0xffff;
data_address_increment_mask_ = 0x00'ff'ff;
continue;
case OperationConstructStackRelativeIndexedIndirect:
data_address_ = registers_.data_bank + data_buffer_.value + registers_.y.full;
data_address_increment_mask_ = 0xff'ff'ff;
data_buffer_.clear();
continue;
case OperationConstructPER:
data_buffer_.value = instruction_buffer_.value + registers_.pc;
data_buffer_.size = 2;
continue;
case OperationPrepareException:
data_buffer_.value = uint32_t((registers_.pc << 8) | get_flags());
if(registers_.emulation_flag) {
if(exception_is_interrupt_) data_buffer_.value &= ~uint32_t(Flag::Break);
data_buffer_.size = 3;
if(pending_exceptions_ & (Reset | PowerOn)) {
registers_.data_bank = 0;
}
++next_op_;
} else {
data_buffer_.value |= registers_.program_bank << 8; // The PBR is always held such that
// PBR+PC produces a 24-bit address;
// therefore a shift by 8 is correct
// here — it matches the shift applied
// to .pc above.
data_buffer_.size = 4;
}
registers_.program_bank = 0;
registers_.flags.inverse_interrupt = 0;
registers_.flags.decimal = 0;
continue;
case OperationPickExceptionVector:
// Priority for abort and reset here is a guess.
if(pending_exceptions_ & (Reset | PowerOn)) {
pending_exceptions_ &= ~(Reset | PowerOn);
data_address_ = 0xfffc;
set_reset_state();
continue;
}
if(pending_exceptions_ & Abort) {
// Special case: restore registers from start of instruction.
registers_ = abort_registers_copy_;
pending_exceptions_ &= ~Abort;
data_address_ = registers_.emulation_flag ? 0xfff8 : 0xffe8;
continue;
}
if(pending_exceptions_ & NMI) {
pending_exceptions_ &= ~NMI;
data_address_ = registers_.emulation_flag ? 0xfffa : 0xffea;
continue;
}
// Last chance saloon for the interrupt process.
if(exception_is_interrupt_) {
data_address_ = registers_.emulation_flag ? 0xfffe : 0xffee;
continue;
}
// ... then this must be a BRK or COP that is being treated as such.
assert((active_instruction_ == instructions) || (active_instruction_ == &instructions[0x02]));
// Test for BRK, given that it has opcode 00.
if(active_instruction_ == instructions) {
data_address_ = registers_.emulation_flag ? 0xfffe : 0xffe6;
} else {
// Implicitly: COP.
data_address_ = registers_.emulation_flag ? 0xfff4 : 0xffe4;
}
continue;
//
// Performance.
//
#define LDA(src) registers_.a.full = (registers_.a.full & registers_.m_masks[0]) | (src & registers_.m_masks[1])
#define LDXY(dest, src) dest = (src) & registers_.x_mask
case OperationPerform:
switch(active_instruction_->operation) {
//
// Loads, stores and transfers (and NOP, and XBA).
//
case LDA:
assert(data_buffer_.size == 2 - m_flag());
LDA(data_buffer_.value);
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case LDX:
assert(data_buffer_.size == 2 - x_flag());
LDXY(registers_.x, data_buffer_.value);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case LDY:
assert(data_buffer_.size == 2 - x_flag());
LDXY(registers_.y, data_buffer_.value);
registers_.flags.set_nz(registers_.y.full, registers_.x_shift);
break;
case PLB:
assert(data_buffer_.size == 1);
registers_.data_bank = (data_buffer_.value & 0xff) << 16;
registers_.flags.set_nz(uint8_t(data_buffer_.value));
break;
case PLD:
assert(data_buffer_.size == 2);
registers_.direct = uint16_t(data_buffer_.value);
registers_.flags.set_nz(uint16_t(data_buffer_.value), 8);
break;
case PLP:
assert(data_buffer_.size == 1);
set_flags(uint8_t(data_buffer_.value));
break;
case STA:
data_buffer_.value = registers_.a.full & registers_.m_masks[1];
data_buffer_.size = 2 - m_flag();
break;
case STZ:
data_buffer_.value = 0;
data_buffer_.size = 2 - m_flag();
break;
case STX:
data_buffer_.value = registers_.x.full;
data_buffer_.size = 2 - x_flag();
break;
case STY:
data_buffer_.value = registers_.y.full;
data_buffer_.size = 2 - x_flag();
break;
case PHB:
data_buffer_.value = registers_.data_bank >> 16;
data_buffer_.size = 1;
break;
case PHK:
data_buffer_.value = registers_.program_bank >> 16;
data_buffer_.size = 1;
break;
case PHD:
data_buffer_.value = registers_.direct;
data_buffer_.size = 2;
break;
case PHP:
data_buffer_.value = get_flags();
data_buffer_.size = 1;
break;
case NOP: break;
case WDM: ++registers_.pc; break;
// The below attempt to obey the 8/16-bit mixed transfer rules
// as documented in https://softpixel.com/~cwright/sianse/docs/65816NFO.HTM
// (and make reasonable guesses as to the N flag).
case TXS:
registers_.s = registers_.x.full;
break;
case TSX:
LDXY(registers_.x, registers_.s.full);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case TXY:
LDXY(registers_.y, registers_.x.full);
registers_.flags.set_nz(registers_.y.full, registers_.x_shift);
break;
case TYX:
LDXY(registers_.x, registers_.y.full);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case TAX:
LDXY(registers_.x, registers_.a.full);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case TAY:
LDXY(registers_.y, registers_.a.full);
registers_.flags.set_nz(registers_.y.full, registers_.x_shift);
break;
case TXA:
LDA(registers_.x.full);
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case TYA:
LDA(registers_.y.full);
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case TCD:
registers_.direct = registers_.a.full;
registers_.flags.set_nz(registers_.a.full, 8);
break;
case TDC:
registers_.a.full = registers_.direct;
registers_.flags.set_nz(registers_.a.full, 8);
break;
case TCS:
registers_.s.full = registers_.a.full;
// No need to worry about byte masking here;
// for the stack it's handled as the emulation runs.
// Cf. the stack_address() macro.
break;
case TSC:
registers_.a.full = stack_address();
registers_.flags.set_nz(registers_.a.full, 8);
break;
case XBA: {
const uint8_t a_low = registers_.a.halves.low;
registers_.a.halves.low = registers_.a.halves.high;
registers_.a.halves.high = a_low;
registers_.flags.set_nz(registers_.a.halves.low);
} break;
//
// Jumps and returns.
//
case JML:
registers_.program_bank = data_buffer_.value & 0xff0000;
registers_.pc = uint16_t(data_buffer_.value);
break;
case JMP:
registers_.pc = uint16_t(instruction_buffer_.value);
break;
case JMPind:
assert(data_buffer_.size == 2);
registers_.pc = uint16_t(data_buffer_.value);
break;
case RTL:
registers_.program_bank = data_buffer_.value & 0xff0000;
[[fallthrough]];
case RTS:
assert(data_buffer_.size == 2 + (active_instruction_->operation == RTL));
registers_.pc = uint16_t(data_buffer_.value + 1);
break;
case JSL:
registers_.program_bank = instruction_buffer_.value & 0xff0000;
[[fallthrough]];
case JSR:
assert(instruction_buffer_.size == 2 + (active_instruction_->operation == JSL));
data_buffer_.value = registers_.pc;
data_buffer_.size = 2;
// The per-cycle scheduling for JSL means that the program
// bank register has already been pushed to the stack by now.
registers_.pc = uint16_t(instruction_buffer_.value);
break;
case RTI:
registers_.pc = uint16_t(data_buffer_.value >> 8);
set_flags(uint8_t(data_buffer_.value));
assert(data_buffer_.size == 4 - registers_.emulation_flag);
if(!registers_.emulation_flag) {
registers_.program_bank = (data_buffer_.value & 0xff000000) >> 8;
}
break;
//
// Block moves.
//
case MVP:
registers_.data_bank = (instruction_buffer_.value & 0xff) << 16;
LDXY(registers_.x.full, registers_.x.full - 1);
LDXY(registers_.y.full, registers_.y.full - 1);
if(registers_.a.full) registers_.pc -= 3;
--registers_.a.full;
break;
case MVN:
registers_.data_bank = (instruction_buffer_.value & 0xff) << 16;
LDXY(registers_.x.full, registers_.x.full + 1);
LDXY(registers_.y.full, registers_.y.full + 1);
if(registers_.a.full) registers_.pc -= 3;
--registers_.a.full;
break;
//
// Flag manipulation.
//
case CLC: registers_.flags.carry = 0; break;
case CLI: registers_.flags.inverse_interrupt = Flag::Interrupt; break;
case CLV: registers_.flags.overflow = 0; break;
case CLD: registers_.flags.decimal = 0; break;
case SEC: registers_.flags.carry = Flag::Carry; break;
case SEI: registers_.flags.inverse_interrupt = 0; break;
case SED: registers_.flags.decimal = Flag::Decimal; break;
case REP:
set_flags(uint8_t(get_flags() &~ instruction_buffer_.value));
break;
case SEP:
set_flags(uint8_t(get_flags() | instruction_buffer_.value));
break;
case XCE: {
const bool old_emulation_flag = registers_.emulation_flag;
set_emulation_mode(registers_.flags.carry);
registers_.flags.carry = old_emulation_flag;
} break;
//
// Increments and decrements.
//
case INC:
assert(data_buffer_.size == 2 - m_flag());
++data_buffer_.value;
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
break;;
case DEC:
assert(data_buffer_.size == 2 - m_flag());
--data_buffer_.value;
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
break;
case INX:
LDXY(registers_.x.full, registers_.x.full + 1);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case DEX:
LDXY(registers_.x.full, registers_.x.full - 1);
registers_.flags.set_nz(registers_.x.full, registers_.x_shift);
break;
case INY:
LDXY(registers_.y.full, registers_.y.full + 1);
registers_.flags.set_nz(registers_.y.full, registers_.x_shift);
break;
case DEY:
LDXY(registers_.y.full, registers_.y.full - 1);
registers_.flags.set_nz(registers_.y.full, registers_.x_shift);
break;
//
// Bitwise operations.
//
case AND:
registers_.a.full &= data_buffer_.value | registers_.m_masks[0];
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case EOR:
registers_.a.full ^= data_buffer_.value;
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case ORA:
registers_.a.full |= data_buffer_.value;
registers_.flags.set_nz(registers_.a.full, registers_.m_shift);
break;
case BIT:
assert(data_buffer_.size == 2 - m_flag());
registers_.flags.set_n(uint16_t(data_buffer_.value), registers_.m_shift);
registers_.flags.set_z(uint16_t(data_buffer_.value & registers_.a.full), registers_.m_shift);
registers_.flags.overflow = (data_buffer_.value >> registers_.m_shift) & Flag::Overflow;
break;
case BITimm:
assert(data_buffer_.size == 2 - m_flag());
registers_.flags.set_z(data_buffer_.value & registers_.a.full, registers_.m_shift);
break;
case TRB:
assert(data_buffer_.size == 2 - m_flag());
registers_.flags.set_z(data_buffer_.value & registers_.a.full, registers_.m_shift);
data_buffer_.value &= ~registers_.a.full;
break;
case TSB:
assert(data_buffer_.size == 2 - m_flag());
registers_.flags.set_z(data_buffer_.value & registers_.a.full, registers_.m_shift);
data_buffer_.value |= registers_.a.full;
break;
//
// Branches.
//
#define BRA(condition) \
assert(instruction_buffer_.size == 1); \
if(!(condition)) { \
next_op_ += 3; \
} else { \
data_buffer_.value = uint32_t(registers_.pc + int8_t(instruction_buffer_.value)); \
data_buffer_.size = 2; \
\
if( \
!registers_.emulation_flag || \
(registers_.pc & 0xff00) == (data_buffer_.value & 0xff00) \
) { \
++next_op_; \
} \
}
case BPL: BRA(!(registers_.flags.negative_result&0x80)); break;
case BMI: BRA(registers_.flags.negative_result&0x80); break;
case BVC: BRA(!registers_.flags.overflow); break;
case BVS: BRA(registers_.flags.overflow); break;
case BCC: BRA(!registers_.flags.carry); break;
case BCS: BRA(registers_.flags.carry); break;
case BNE: BRA(registers_.flags.zero_result); break;
case BEQ: BRA(!registers_.flags.zero_result); break;
case BRA: BRA(true); break;
#undef BRA
case BRL:
assert(instruction_buffer_.size == 2);
registers_.pc += int16_t(instruction_buffer_.value);
break;
//
// Shifts and rolls.
//
case ASL:
registers_.flags.carry = uint8_t(data_buffer_.value >> (7 + registers_.m_shift));
data_buffer_.value <<= 1;
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
break;
case LSR:
registers_.flags.carry = uint8_t(data_buffer_.value & 1);
data_buffer_.value >>= 1;
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
break;
case ROL:
data_buffer_.value = (data_buffer_.value << 1) | registers_.flags.carry;
registers_.flags.carry = uint8_t(data_buffer_.value >> (8 + registers_.m_shift));
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
break;
case ROR: {
const uint8_t next_carry = data_buffer_.value & 1;
data_buffer_.value = (data_buffer_.value >> 1) | (uint32_t(registers_.flags.carry) << (7 + registers_.m_shift));
registers_.flags.carry = next_carry;
registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
} break;
//
// Arithmetic.
//
#define cp(v, shift, mask) {\
const uint32_t temp32 = (v.full & mask) - (data_buffer_.value & mask); \
registers_.flags.set_nz(uint16_t(temp32), shift); \
registers_.flags.carry = ((~temp32) >> (8 + shift))&1; \
}
case CMP: cp(registers_.a, registers_.m_shift, registers_.m_masks[1]); break;
case CPX: cp(registers_.x, registers_.x_shift, registers_.x_mask); break;
case CPY: cp(registers_.y, registers_.x_shift, registers_.x_mask); break;
#undef cp
// As implemented below, both ADC and SBC apply the 6502 test for overflow (i.e. based
// on intermediate results) rather than the 65C02 (i.e. based on the final result).
// This tracks the online tests I found, which hail from Nintendo world. So I'm currently
// unclear whether this is correct or merely a figment of Nintendo's custom chip.
case SBC:
if(registers_.flags.decimal) {
const uint16_t a = registers_.a.full & registers_.m_masks[1];
data_buffer_.value = ~data_buffer_.value & registers_.m_masks[1];
int result = registers_.flags.carry;
uint16_t partials = 0;
#define nibble(mask, adjustment, carry) \
result += (a & mask) + (data_buffer_.value & mask); \
partials += result & mask; \
result -= ((result - carry) >> 16) & adjustment; \
result &= (carry & ~(result >> 1)) | (carry - 1);
// i.e. add the next nibble to that in the accumulator, with carry, and
// store it to result. Keep a copy for the partials.
//
// If result is less than carry, subtract adjustment.
//
// Allow onward carry if the bit immediately above this nibble is 1, and
// the current partial result is positive.
nibble(0x000f, 0x0006, 0x00010);
nibble(0x00f0, 0x0060, 0x00100);
nibble(0x0f00, 0x0600, 0x01000);
nibble(0xf000, 0x6000, 0x10000);
#undef nibble
registers_.flags.overflow = (( (partials ^ registers_.a.full) & (partials ^ data_buffer_.value) ) >> (1 + registers_.m_shift))&0x40;
registers_.flags.set_nz(uint16_t(result), registers_.m_shift);
registers_.flags.carry = (result >> (8 + registers_.m_shift))&1;
LDA(result);
break;
}
data_buffer_.value = ~data_buffer_.value & registers_.m_masks[1];
[[fallthrough]];
case ADC: {
int result;
const uint16_t a = registers_.a.full & registers_.m_masks[1];
if(registers_.flags.decimal) {
uint16_t partials = 0;
result = registers_.flags.carry;
#define nibble(mask, limit, adjustment, carry) \
result += (a & mask) + (data_buffer_.value & mask); \
partials += result & mask; \
if(result >= limit) result = ((result + adjustment) & (carry - 1)) + carry;
nibble(0x000f, 0x000a, 0x0006, 0x00010);
nibble(0x00f0, 0x00a0, 0x0060, 0x00100);
nibble(0x0f00, 0x0a00, 0x0600, 0x01000);
nibble(0xf000, 0xa000, 0x6000, 0x10000);
#undef nibble
registers_.flags.overflow = (( (partials ^ registers_.a.full) & (partials ^ data_buffer_.value) ) >> (1 + registers_.m_shift))&0x40;
} else {
result = int(a + data_buffer_.value + registers_.flags.carry);
registers_.flags.overflow = (( (uint16_t(result) ^ registers_.a.full) & (uint16_t(result) ^ data_buffer_.value) ) >> (1 + registers_.m_shift))&0x40;
}
registers_.flags.set_nz(uint16_t(result), registers_.m_shift);
registers_.flags.carry = (result >> (8 + registers_.m_shift))&1;
LDA(result);
} break;
//
// STP and WAI
//
case STP:
required_exceptions_ = Reset;
break;
case WAI:
required_exceptions_ = Reset | IRQ | NMI;
break;
}
continue;
}
// Store a selection as to the exceptions, if any, that would be honoured after this cycle if the
// next thing is a MoveToNextProgram.
selected_exceptions_ = pending_exceptions_ & (registers_.flags.inverse_interrupt | PowerOn | Reset | NMI);
number_of_cycles -= bus_handler_.perform_bus_operation(bus_operation_, static_cast<typename BusHandler::AddressType>(bus_address_), bus_value_);
}
}
#undef LDA
#undef LDXY
#undef read
#undef write
#undef bus_operation
#undef x
#undef y
#undef m_flag
#undef x_flag
#undef stack_address
cycles_left_to_run_ = number_of_cycles;
}
void ProcessorBase::set_power_on(bool active) {
if(active) {
pending_exceptions_ |= PowerOn;
} else {
pending_exceptions_ &= ~PowerOn;
selected_exceptions_ &= ~PowerOn;
}
}
void ProcessorBase::set_irq_line(bool active) {
if(active) {
pending_exceptions_ |= IRQ;
} else {
pending_exceptions_ &= ~IRQ;
}
}
void ProcessorBase::set_reset_line(bool active) {
if(active) {
pending_exceptions_ |= Reset;
} else {
pending_exceptions_ &= ~Reset;
}
}
void ProcessorBase::set_nmi_line(bool active) {
// This is edge triggered.
if(active) {
pending_exceptions_ |= NMI;
}
}
void ProcessorBase::set_abort_line(bool active) {
// Take a copy of register state now to restore at the beginning of the exception
// if abort has gone active, preparing to regress the program counter.
if(active) {
pending_exceptions_ |= Abort;
abort_registers_copy_ = registers_;
abort_registers_copy_.pc = last_operation_pc_;
} else {
pending_exceptions_ &= ~Abort;
}
}
template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler, uses_ready_line>::set_ready_line(bool active) {
assert(uses_ready_line);
ready_line_ = active;
}
// The 65816 can't jam.
bool ProcessorBase::is_jammed() const { return false; }
bool ProcessorBase::get_is_resetting() const {
return pending_exceptions_ & (Reset | PowerOn);
}
int ProcessorBase::get_extended_bus_output() {
return
(memory_lock_ ? ExtendedBusOutput::MemoryLock : 0) |
(registers_.mx_flags[0] ? ExtendedBusOutput::MemorySize : 0) |
(registers_.mx_flags[1] ? ExtendedBusOutput::IndexSize : 0) |
(registers_.emulation_flag ? ExtendedBusOutput::Emulation : 0);
}
void ProcessorBase::restart_operation_fetch() {
// Find a OperationMoveToNextProgram, so that the main loop can make
// relevant decisions.
next_op_ = micro_ops_.data();
while(*next_op_ != OperationMoveToNextProgram) ++next_op_;
}
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