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64 lines
1.8 KiB
C++
64 lines
1.8 KiB
C++
//
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// Decoder.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 10/04/2022.
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// Copyright © 2022 Thomas Harte. All rights reserved.
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//
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#ifndef Decoder_hpp
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#define Decoder_hpp
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#include "Instruction.hpp"
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namespace InstructionSet {
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namespace M68k {
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/*!
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A stateless decoder that can map from instruction words to preinstructions
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(i.e. enough to know the operation and size, and either know the addressing mode
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and registers or else know how many further extension words are needed).
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*/
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class Predecoder {
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public:
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Preinstruction decode(uint16_t instruction);
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private:
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// Page by page decoders; each gets a bit ad hoc so
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// it is neater to separate them.
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Preinstruction decode0(uint16_t instruction);
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Preinstruction decode1(uint16_t instruction);
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Preinstruction decode2(uint16_t instruction);
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Preinstruction decode3(uint16_t instruction);
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Preinstruction decode4(uint16_t instruction);
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Preinstruction decode5(uint16_t instruction);
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Preinstruction decode6(uint16_t instruction);
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Preinstruction decode7(uint16_t instruction);
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Preinstruction decode8(uint16_t instruction);
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Preinstruction decode9(uint16_t instruction);
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Preinstruction decodeA(uint16_t instruction);
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Preinstruction decodeB(uint16_t instruction);
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Preinstruction decodeC(uint16_t instruction);
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Preinstruction decodeD(uint16_t instruction);
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Preinstruction decodeE(uint16_t instruction);
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Preinstruction decodeF(uint16_t instruction);
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// Specific instruction decoders.
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template <uint8_t operation> Preinstruction decode(uint16_t instruction);
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enum ExtendedOperation {
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MOVEMtoRl = uint8_t(Operation::Max), MOVEMtoRw,
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MOVEMtoMl, MOVEMtoMw,
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MOVEPtoRl, MOVEPtoRw,
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MOVEPtoMl, MOVEPtoMw,
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};
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static constexpr Operation operation(uint8_t op);
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};
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}
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}
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#endif /* Decoder_hpp */
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