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95 lines
2.6 KiB
C++
95 lines
2.6 KiB
C++
//
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// 68000Mk2Storage.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 16/05/2022.
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// Copyright © 2022 Thomas Harte. All rights reserved.
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//
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#ifndef _8000Mk2Storage_h
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#define _8000Mk2Storage_h
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#include "../../../InstructionSets/M68k/Status.hpp"
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#include "../../../InstructionSets/M68k/Decoder.hpp"
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namespace CPU {
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namespace MC68000Mk2 {
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struct ProcessorBase {
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/// States for the state machine which are named by
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/// me for their purpose rather than automatically by file position.
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/// These are negative to avoid ambiguity with the other group.
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enum State: int {
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Reset = -1,
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Decode = -2,
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WaitForDTACK = -3,
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FetchOperand = -4,
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// Various different effective address calculations.
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CalculateAnDn = -5,
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// Various forms of perform; each of these will
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// perform the current instruction, then do the
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// indicated bus cycle.
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Perform_np = -6,
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};
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int state_ = State::Reset;
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/// Counts time left on the clock before the current batch of processing
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/// is complete; may be less than zero.
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HalfCycles time_remaining_;
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/// Current supervisor state, for direct provision to the bus handler.
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int is_supervisor_ = 1;
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// A decoder for instructions, plus all collected information about the
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// current instruction.
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InstructionSet::M68k::Predecoder<InstructionSet::M68k::Model::M68000> decoder_;
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InstructionSet::M68k::Preinstruction instruction_;
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uint16_t opcode_;
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uint8_t operand_flags_;
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uint32_t instruction_address_;
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// Register state.
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InstructionSet::M68k::Status status_;
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SlicedInt32 program_counter_;
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SlicedInt32 registers_[16]; // D0–D7 followed by A0–A7.
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SlicedInt32 stack_pointers_[2];
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/// Current state of the DTACK input.
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bool dtack_ = false;
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/// Current state of the VPA input.
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bool vpa_ = false;
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/// Current state of the BERR input.
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bool berr_ = false;
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/// Contains the prefetch queue; the most-recently fetched thing is the
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/// low portion of this word, and the thing fetched before that has
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/// proceeded to the high portion.
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SlicedInt32 prefetch_;
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// Temporary storage for the current instruction's operands
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// and the corresponding effective addresses.
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CPU::SlicedInt32 operand_[2];
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uint32_t effective_address_[2];
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/// If currently in the wait-for-DTACK state, this indicates where to go
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/// upon receipt of DTACK or VPA. BERR will automatically segue
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/// into the proper exception.
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int post_dtack_state_ = 0;
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/// The perform state for this operation.
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int perform_state_ = 0;
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/// When fetching or storing operands, this is the next one to fetch
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/// or store.
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int next_operand_ = 0;
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};
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}
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}
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#endif /* _8000Mk2Storage_h */
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