// // 68000Implementation.hpp // Clock Signal // // Created by Thomas Harte on 10/03/2019. // Copyright © 2019 Thomas Harte. All rights reserved. // #define get_status() \ ( \ (carry_flag_ ? 0x0001 : 0x0000) | \ (overflow_flag_ ? 0x0002 : 0x0000) | \ (zero_result_ ? 0x0000 : 0x0004) | \ (negative_flag_ ? 0x0008 : 0x0000) | \ (extend_flag_ ? 0x0010 : 0x0000) | \ (interrupt_level_ << 8) | \ (trace_flag_ ? 0x8000 : 0x0000) | \ (is_supervisor_ << 13) \ ) #define set_status(x) \ carry_flag_ = (x) & 0x0001; \ overflow_flag_ = (x) & 0x0002; \ zero_result_ = ((x) & 0x0004) ^ 0x0004; \ negative_flag_ = (x) & 0x0008; \ extend_flag_ = (x) & 0x0010; \ interrupt_level_ = ((x) >> 8) & 7; \ trace_flag_ = (x) & 0x8000; \ is_supervisor_ = ((x) >> 13) & 1; template void Processor::run_for(HalfCycles duration) { HalfCycles remaining_duration = duration + half_cycles_left_to_run_; while(remaining_duration > HalfCycles(0)) { /* FIND THE NEXT MICRO-OP IF UNKNOWN. */ if(active_step_->is_terminal()) { while(true) { // If there are any more micro-operations available, just move onwards. if(active_micro_op_ && !active_micro_op_->is_terminal()) { ++active_micro_op_; } else { // Either the micro-operations for this instruction have been exhausted, or // no instruction was ongoing. Either way, do a standard instruction operation. // TODO: unless an interrupt is pending, or the trap flag is set. const uint16_t next_instruction = prefetch_queue_.halves.high.full; if(!instructions[next_instruction].micro_operations) { // TODO: once all instructions are implemnted, this should be an instruction error. std::cerr << "68000 Abilities exhausted; can't manage instruction " << std::hex << next_instruction << " from " << (program_counter_.full - 4) << std::endl; return; } else { std::cout << "Performing " << std::hex << next_instruction << " from " << (program_counter_.full - 4) << std::endl; } active_program_ = &instructions[next_instruction]; active_micro_op_ = active_program_->micro_operations; } switch(active_micro_op_->action) { default: std::cerr << "Unhandled 68000 micro op action " << std::hex << active_micro_op_->action << std::endl; break; case int(MicroOp::Action::None): break; case int(MicroOp::Action::PerformOperation): switch(active_program_->operation) { /* ABCD adds the lowest bytes form the source and destination using BCD arithmetic, obeying the extend flag. */ case Operation::ABCD: { // Pull out the two halves, for simplicity. const uint8_t source = active_program_->source->halves.low.halves.low; const uint8_t destination = active_program_->destination->halves.low.halves.low; // Perform the BCD add by evaluating the two nibbles separately. int result = (destination & 0xf) + (source & 0xf) + (extend_flag_ ? 1 : 0); if(result > 0x09) result += 0x06; result += (destination & 0xf0) + (source & 0xf0); if(result > 0x99) result += 0x60; // Set all flags essentially as if this were normal addition. zero_result_ |= result & 0xff; extend_flag_ = carry_flag_ = result & ~0xff; negative_flag_ = result & 0x80; overflow_flag_ = ~(source ^ destination) & (destination ^ result) & 0x80; // Store the result. active_program_->destination->halves.low.halves.low = uint8_t(result); } break; // ADD and ADDA add two quantities, the latter sign extending and without setting any flags. case Operation::ADDb: { const uint8_t source = active_program_->source->halves.low.halves.low; const uint8_t destination = active_program_->destination->halves.low.halves.low; const int result = destination + source; zero_result_ = active_program_->destination->halves.low.halves.low = uint8_t(result); extend_flag_ = carry_flag_ = result & ~0xff; negative_flag_ = result & 0x80; overflow_flag_ = ~(source ^ destination) & (destination ^ result) & 0x80; } break; case Operation::ADDw: { const uint16_t source = active_program_->source->halves.low.full; const uint16_t destination = active_program_->destination->halves.low.full; const int result = destination + source; zero_result_ = active_program_->destination->halves.low.full = uint16_t(result); extend_flag_ = carry_flag_ = result & ~0xffff; negative_flag_ = result & 0x8000; overflow_flag_ = ~(source ^ destination) & (destination ^ result) & 0x8000; } break; case Operation::ADDl: { const uint32_t source = active_program_->source->full; const uint32_t destination = active_program_->destination->full; const uint64_t result = destination + source; zero_result_ = active_program_->destination->halves.low.full = uint32_t(result); extend_flag_ = carry_flag_ = result >> 32; negative_flag_ = result & 0x80000000; overflow_flag_ = ~(source ^ destination) & (destination ^ result) & 0x80000000; } break; case Operation::ADDAw: active_program_->destination->full += int16_t(active_program_->source->halves.low.full); break; case Operation::ADDAl: active_program_->destination->full += active_program_->source->full; break; // BRA: alters the program counter, exclusively via the prefetch queue. case Operation::BRA: { const int8_t byte_offset = int8_t(prefetch_queue_.halves.high.halves.low); // A non-zero offset byte branches by just that amount; otherwise use the word // after as an offset. In both cases, treat as signed. if(byte_offset) { program_counter_.full = (program_counter_.full + byte_offset) - 2; } else { program_counter_.full += int16_t(prefetch_queue_.halves.low.full); } } break; // Bcc: evaluates the relevant condition and displacement size and then: // if condition is false, schedules bus operations to get past this instruction; // otherwise applies the offset and schedules bus operations to refill the prefetch queue. case Operation::Bcc: { // Grab the 8-bit offset. const int8_t byte_offset = int8_t(prefetch_queue_.halves.high.halves.low); // Test the conditional. bool should_branch; switch(prefetch_queue_.halves.high.halves.high & 0xf) { default: case 0x00: should_branch = true; break; // true case 0x01: should_branch = false; break; // false case 0x02: should_branch = zero_result_ && !carry_flag_; break; // high case 0x03: should_branch = !zero_result_ || carry_flag_; break; // low or same case 0x04: should_branch = !carry_flag_; break; // carry clear case 0x05: should_branch = carry_flag_; break; // carry set case 0x06: should_branch = zero_result_; break; // not equal case 0x07: should_branch = !zero_result_; break; // equal case 0x08: should_branch = !overflow_flag_; break; // overflow clear case 0x09: should_branch = overflow_flag_; break; // overflow set case 0x0a: should_branch = !negative_flag_; break; // positive case 0x0b: should_branch = negative_flag_; break; // negative case 0x0c: should_branch = (negative_flag_ && overflow_flag_) || (!negative_flag_ && !overflow_flag_); break; // greater than or equal case 0x0d: should_branch = (negative_flag_ || !overflow_flag_) && (!negative_flag_ || overflow_flag_); break; // less than case 0x0e: should_branch = zero_result_ && ((negative_flag_ && overflow_flag_) || (!negative_flag_ && !overflow_flag_)); break; // greater than case 0x0f: should_branch = (!zero_result_ || negative_flag_) && (!overflow_flag_ || !negative_flag_) && overflow_flag_; break; // less than or equal } // Schedule something appropriate, by rewriting the program for this instruction temporarily. if(should_branch) { if(byte_offset) { program_counter_.full = (program_counter_.full + byte_offset) - 2; // - 2 because this should be calculated from the high word of the prefetch. } else { program_counter_.full += int16_t(prefetch_queue_.halves.low.full); } active_micro_op_->bus_program = branch_taken_bus_steps_; } else { if(byte_offset) { active_micro_op_->bus_program = branch_byte_not_taken_bus_steps_; } else { active_micro_op_->bus_program = branch_word_not_taken_bus_steps_; } } } break; /* CMP.b, CMP.l and CMP.w: sets the condition flags (other than extend) based on a subtraction of the source from the destination; the result of the subtraction is not stored. */ case Operation::CMPb: { const uint8_t source = active_program_->source->halves.low.halves.low; const uint8_t destination = active_program_->destination->halves.low.halves.low; const int result = destination - source; zero_result_ = result & 0xff; carry_flag_ = result & ~0xff; negative_flag_ = result & 0x80; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x80; } break; case Operation::CMPw: { const uint16_t source = active_program_->source->halves.low.full; const uint16_t destination = active_program_->destination->halves.low.full; const int result = destination - source; zero_result_ = result & 0xffff; carry_flag_ = result & ~0xffff; negative_flag_ = result & 0x8000; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x8000; } break; case Operation::CMPl: { const uint32_t source = active_program_->source->full; const uint32_t destination = active_program_->destination->full; const uint64_t result = destination - source; zero_result_ = uint32_t(result); carry_flag_ = result >> 32; negative_flag_ = result & 0x80000000; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x80000000; } break; // JMP: copies the source to the program counter. case Operation::JMP: program_counter_.full = active_program_->source->full; break; /* MOVE.b, MOVE.l and MOVE.w: move the least significant byte or word, or the entire long word, and set negative, zero, overflow and carry as appropriate. */ case Operation::MOVEb: zero_result_ = active_program_->destination->halves.low.halves.low = active_program_->source->halves.low.halves.low; negative_flag_ = zero_result_ & 0x80; overflow_flag_ = carry_flag_ = 0; break; case Operation::MOVEw: zero_result_ = active_program_->destination->halves.low.full = active_program_->source->halves.low.full; negative_flag_ = zero_result_ & 0x8000; overflow_flag_ = carry_flag_ = 0; break; case Operation::MOVEl: zero_result_ = active_program_->destination->full = active_program_->source->full; negative_flag_ = zero_result_ & 0x80000000; overflow_flag_ = carry_flag_ = 0; break; /* MOVE.q: a single byte is moved from the current instruction, and sign extended. */ case Operation::MOVEq: zero_result_ = active_program_->destination->full = prefetch_queue_.halves.high.halves.low; negative_flag_ = zero_result_ & 0x80; overflow_flag_ = carry_flag_ = 0; active_program_->destination->full |= negative_flag_ ? 0xffffff00 : 0; break; /* MOVEA.l: move the entire long word; MOVEA.w: move the least significant word and sign extend it. Neither sets any flags. */ case Operation::MOVEAw: active_program_->destination->halves.low.full = active_program_->source->halves.low.full; active_program_->destination->halves.high.full = (active_program_->destination->halves.low.full & 0x8000) ? 0xffff : 0; break; case Operation::MOVEAl: active_program_->destination->full = active_program_->source->full; break; /* Status word moves. */ case Operation::MOVEtoSR: set_status(active_program_->source->full); break; case Operation::MOVEfromSR: active_program_->source->halves.low.full = get_status(); break; /* The no-op. */ case Operation::None: break; /* SBCD subtracts the lowest byte of the source from that of the destination using BCD arithmetic, obeying the extend flag. */ case Operation::SBCD: { // Pull out the two halves, for simplicity. const uint8_t source = active_program_->source->halves.low.halves.low; const uint8_t destination = active_program_->destination->halves.low.halves.low; // Perform the BCD add by evaluating the two nibbles separately. int result = (destination & 0xf) - (source & 0xf) - (extend_flag_ ? 1 : 0); if(result > 0x09) result -= 0x06; result += (destination & 0xf0) - (source & 0xf0); if(result > 0x99) result -= 0x60; // Set all flags essentially as if this were normal subtraction. zero_result_ |= result & 0xff; extend_flag_ = carry_flag_ = result & ~0xff; negative_flag_ = result & 0x80; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x80; // Store the result. active_program_->destination->halves.low.halves.low = uint8_t(result); } break; case Operation::SUBb: { const uint8_t source = active_program_->source->halves.low.halves.low; const uint8_t destination = active_program_->destination->halves.low.halves.low; const int result = destination - source; zero_result_ = active_program_->destination->halves.low.halves.low = uint8_t(result); extend_flag_ = carry_flag_ = result & ~0xff; negative_flag_ = result & 0x80; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x80; } break; case Operation::SUBw: { const uint16_t source = active_program_->source->halves.low.full; const uint16_t destination = active_program_->destination->halves.low.full; const int result = destination - source; zero_result_ = active_program_->destination->halves.low.full = uint16_t(result); extend_flag_ = carry_flag_ = result & ~0xffff; negative_flag_ = result & 0x8000; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x8000; } break; case Operation::SUBl: { const uint32_t source = active_program_->source->full; const uint32_t destination = active_program_->destination->full; const uint64_t result = destination - source; zero_result_ = active_program_->destination->halves.low.full = uint32_t(result); extend_flag_ = carry_flag_ = result >> 32; negative_flag_ = result & 0x80000000; overflow_flag_ = (source ^ destination) & (destination ^ result) & 0x80000000; } break; case Operation::SUBAw: active_program_->destination->full -= int16_t(active_program_->source->halves.low.full); break; case Operation::SUBAl: active_program_->destination->full -= active_program_->source->full; break; /* Development period debugging. */ default: std::cerr << "Should do something with program operation " << int(active_program_->operation) << std::endl; break; } break; case int(MicroOp::Action::SetMoveFlagsb): zero_result_ = active_program_->source->halves.low.halves.low; negative_flag_ = zero_result_ & 0x80; overflow_flag_ = carry_flag_ = 0; break; case int(MicroOp::Action::SetMoveFlagsw): zero_result_ = active_program_->source->halves.low.full; negative_flag_ = zero_result_ & 0x8000; overflow_flag_ = carry_flag_ = 0; break; case int(MicroOp::Action::SetMoveFlagsl): zero_result_ = active_program_->source->full; negative_flag_ = zero_result_ & 0x80000000; overflow_flag_ = carry_flag_ = 0; break; case int(MicroOp::Action::Decrement1): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full -= 1; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full -= 1; break; case int(MicroOp::Action::Decrement2): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full -= 2; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full -= 2; break; case int(MicroOp::Action::Decrement4): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full -= 4; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full -= 4; break; case int(MicroOp::Action::Increment1): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full += 1; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full += 1; break; case int(MicroOp::Action::Increment2): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full += 2; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full += 2; break; case int(MicroOp::Action::Increment4): if(active_micro_op_->action & MicroOp::SourceMask) active_program_->source_address->full += 4; if(active_micro_op_->action & MicroOp::DestinationMask) active_program_->destination_address->full += 4; break; case int(MicroOp::Action::SignExtendWord): if(active_micro_op_->action & MicroOp::SourceMask) { active_program_->source->halves.high.full = (active_program_->source->halves.low.full & 0x8000) ? 0xffff : 0x0000; } if(active_micro_op_->action & MicroOp::DestinationMask) { active_program_->destination->halves.high.full = (active_program_->destination->halves.low.full & 0x8000) ? 0xffff : 0x0000; } break; case int(MicroOp::Action::SignExtendByte): if(active_micro_op_->action & MicroOp::SourceMask) { active_program_->source->full = (active_program_->source->full & 0xff) | (active_program_->source->full & 0x80) ? 0xffffff : 0x000000; } if(active_micro_op_->action & MicroOp::DestinationMask) { active_program_->destination->full = (active_program_->destination->full & 0xff) | (active_program_->destination->full & 0x80) ? 0xffffff : 0x000000; } break; case int(MicroOp::Action::CalcD16PC) | MicroOp::SourceMask: effective_address_[0] = int16_t(prefetch_queue_.halves.low.full) + program_counter_.full; break; case int(MicroOp::Action::CalcD16PC) | MicroOp::DestinationMask: effective_address_[1] = int16_t(prefetch_queue_.halves.low.full) + program_counter_.full; break; case int(MicroOp::Action::CalcD16PC) | MicroOp::SourceMask | MicroOp::DestinationMask: effective_address_[0] = int16_t(prefetch_queue_.halves.high.full) + program_counter_.full; effective_address_[1] = int16_t(prefetch_queue_.halves.low.full) + program_counter_.full; break; case int(MicroOp::Action::CalcD16An) | MicroOp::SourceMask: effective_address_[0] = int16_t(prefetch_queue_.halves.low.full) + active_program_->source->full; break; case int(MicroOp::Action::CalcD16An) | MicroOp::DestinationMask: effective_address_[1] = int16_t(prefetch_queue_.halves.low.full) + active_program_->destination->full; break; case int(MicroOp::Action::CalcD16An) | MicroOp::SourceMask | MicroOp::DestinationMask: effective_address_[0] = int16_t(prefetch_queue_.halves.high.full) + active_program_->source->full; effective_address_[1] = int16_t(prefetch_queue_.halves.low.full) + active_program_->destination->full; break; #define CalculateD8AnXn(data, source, target) {\ const auto register_index = (data.full >> 12) & 7; \ const RegisterPair32 &displacement = (data.full & 0x8000) ? address_[register_index] : data_[register_index]; \ target.full = int8_t(data.halves.low) + source->full; \ \ if(data.full & 0x800) { \ target.full += displacement.halves.low.full; \ } else { \ target.full += displacement.full; \ } \ } case int(MicroOp::Action::CalcD8AnXn) | MicroOp::SourceMask: { CalculateD8AnXn(prefetch_queue_.halves.low, active_program_->source, effective_address_[0]); } break; case int(MicroOp::Action::CalcD8AnXn) | MicroOp::DestinationMask: { CalculateD8AnXn(prefetch_queue_.halves.low, active_program_->destination, effective_address_[1]); } break; case int(MicroOp::Action::CalcD8AnXn) | MicroOp::SourceMask | MicroOp::DestinationMask: { CalculateD8AnXn(prefetch_queue_.halves.high, active_program_->source, effective_address_[0]); CalculateD8AnXn(prefetch_queue_.halves.low, active_program_->destination, effective_address_[1]); } break; #undef CalculateD8AnXn case int(MicroOp::Action::AssembleWordAddressFromPrefetch) | MicroOp::SourceMask: // Assumption: this will be assembling right at the start of the instruction. effective_address_[0] = prefetch_queue_.halves.low.full; break; case int(MicroOp::Action::AssembleWordAddressFromPrefetch) | MicroOp::DestinationMask: effective_address_[1] = prefetch_queue_.halves.low.full; break; case int(MicroOp::Action::AssembleLongWordAddressFromPrefetch) | MicroOp::SourceMask: effective_address_[0] = prefetch_queue_.full; break; case int(MicroOp::Action::AssembleLongWordAddressFromPrefetch) | MicroOp::DestinationMask: effective_address_[1] = prefetch_queue_.full; break; case int(MicroOp::Action::AssembleWordDataFromPrefetch) | MicroOp::SourceMask: // Assumption: this will be assembling right at the start of the instruction. source_bus_data_[0] = prefetch_queue_.halves.low.full; break; case int(MicroOp::Action::AssembleWordDataFromPrefetch) | MicroOp::DestinationMask: destination_bus_data_[0] = prefetch_queue_.halves.low.full; break; case int(MicroOp::Action::AssembleLongWordDataFromPrefetch) | MicroOp::SourceMask: source_bus_data_[0] = prefetch_queue_.full; break; case int(MicroOp::Action::AssembleLongWordDataFromPrefetch) | MicroOp::DestinationMask: destination_bus_data_[0] = prefetch_queue_.full; break; case int(MicroOp::Action::CopyToEffectiveAddress) | MicroOp::SourceMask: effective_address_[0] = *active_program_->source; break; case int(MicroOp::Action::CopyToEffectiveAddress) | MicroOp::DestinationMask: effective_address_[1] = *active_program_->destination; break; case int(MicroOp::Action::CopyToEffectiveAddress) | MicroOp::SourceMask | MicroOp::DestinationMask: effective_address_[0] = *active_program_->source; effective_address_[1] = *active_program_->destination; break; } // If we've got to a micro-op that includes bus steps, break out of this loop. if(!active_micro_op_->is_terminal()) { active_step_ = active_micro_op_->bus_program; break; } } } /* PERFORM THE CURRENT BUS STEP'S MICROCYCLE. */ // Check for DTack if this isn't being treated implicitly. if(!dtack_is_implicit) { if(active_step_->microcycle.data_select_active() && !dtack_) { // TODO: perform wait state. continue; } } // TODO: synchronous bus. // TODO: check for bus error. // Perform the microcycle. remaining_duration -= active_step_->microcycle.length + bus_handler_.perform_bus_operation(active_step_->microcycle, is_supervisor_); /* PERFORM THE BUS STEP'S ACTION. */ switch(active_step_->action) { default: std::cerr << "Unimplemented 68000 bus step action: " << int(active_step_->action) << std::endl; return; break; case BusStep::Action::None: break; case BusStep::Action::IncrementEffectiveAddress0: effective_address_[0].full += 2; break; case BusStep::Action::IncrementEffectiveAddress1: effective_address_[1].full += 2; break; case BusStep::Action::DecrementEffectiveAddress0: effective_address_[0].full -= 2; break; case BusStep::Action::DecrementEffectiveAddress1: effective_address_[1].full -= 2; break; case BusStep::Action::IncrementProgramCounter: program_counter_.full += 2; break; case BusStep::Action::AdvancePrefetch: prefetch_queue_.halves.high = prefetch_queue_.halves.low; break; } // Move to the next bus step. ++ active_step_; } half_cycles_left_to_run_ = remaining_duration; } template ProcessorState Processor::get_state() { write_back_stack_pointer(); State state; memcpy(state.data, data_, sizeof(state.data)); memcpy(state.address, address_, sizeof(state.address)); state.user_stack_pointer = stack_pointers_[0].full; state.supervisor_stack_pointer = stack_pointers_[1].full; state.status = get_status(); return state; } template void Processor::set_state(const ProcessorState &state) { memcpy(data_, state.data, sizeof(state.data)); memcpy(address_, state.address, sizeof(state.address)); stack_pointers_[0].full = state.user_stack_pointer; stack_pointers_[1].full = state.supervisor_stack_pointer; set_status(state.status); address_[7] = stack_pointers_[is_supervisor_]; } #undef get_status #undef set_status