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https://github.com/MoleskiCoder/EightBit.git
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127 lines
3.4 KiB
C++
127 lines
3.4 KiB
C++
#pragma once
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// Uses some information from:
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// http://www.cpu-world.com/Arch/6809.html
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#include <cstdint>
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#include <Bus.h>
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#include <BigEndianProcessor.h>
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namespace EightBit {
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class mc6809 : public BigEndianProcessor {
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public:
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enum StatusBits {
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// Entire flag: set if the complete machine state was saved in the stack.
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// If this bit is not set then only program counter and condition code
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// registers were saved in the stack. This bit is used by interrupt
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// handling routines only.
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// The bit is cleared by fast interrupts, and set by all other interrupts.
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EF = Bit7,
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// Fast interrupt mask: set if the FIRQ interrupt is disabled.
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FF = Bit6,
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// Half carry: set if there was a carry from bit 3 to bit 4 of the result
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// during the last add operation.
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HF = Bit5,
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// Interrupt mask: set if the IRQ interrupt is disabled.
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IF = Bit4,
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// Negative: set if the most significant bit of the result is set.
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// This bit can be set not only by arithmetic and logical operations,
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// but also by load / store operations.
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NF = Bit3,
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// Zero: set if the result is zero. Like the N bit, this bit can be
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// set not only by arithmetic and logical operations, but also
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// by load / store operations.
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ZF = Bit2,
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// Overflow: set if there was an overflow during last result calculation.
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// Logical, load and store operations clear this bit.
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VF = Bit1,
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// Carry: set if there was a carry from the bit 7 during last add
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// operation, or if there was a borrow from last subtract operation,
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// or if bit 7 of the A register was set during last MUL operation.
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CF = Bit0,
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};
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mc6809(Bus& bus);
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Signal<mc6809> ExecutingInstruction;
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Signal<mc6809> ExecutedInstruction;
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virtual int execute(uint8_t opcode) final;
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virtual int step() final;
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virtual void powerOn() final;
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register16_t& D() { return m_d; }
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uint8_t& A() { return D().high; }
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uint8_t& B() { return D().low; }
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register16_t& X() { return m_x; }
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register16_t& Y() { return m_y; }
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register16_t& U() { return m_u; }
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register16_t& S() { return m_s; }
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uint8_t& DP() { return m_dp; }
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uint8_t& CC() { return m_cc; }
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PinLevel& IRQ() { return INT(); }
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PinLevel& FIRQ() { return m_firq; }
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protected:
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virtual void reset() final;
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private:
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const uint8_t RESETvector = 0xfe;
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const uint8_t NMIvector = 0xfc;
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const uint8_t SWIvector = 0xfa;
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const uint8_t IRQvector = 0xf8;
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const uint8_t FIRQvector = 0xf6;
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const uint8_t SWI2vector = 0xf4;
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const uint8_t SWI3vector = 0xf2;
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const uint8_t RESERVEDvector = 0xf0;
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// Register selection for "indexed"
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register16_t& RR(int which);
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// Addressing modes
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void Address_direct();
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void Address_indexed();
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void Address_extended();
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// Addressing mode readers
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uint8_t AM_immediate_byte();
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uint8_t AM_direct_byte();
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uint8_t AM_indexed_byte();
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uint8_t AM_extended_byte();
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register16_t AM_immediate_word();
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register16_t AM_direct_word();
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register16_t AM_indexed_word();
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register16_t AM_extended_word();
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void abx();
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uint8_t adc(uint8_t operand, uint8_t data);
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uint8_t add(uint8_t operand, uint8_t data, int carry = 0);
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register16_t add(register16_t operand, register16_t data);
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uint8_t andr(uint8_t operand, uint8_t data);
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uint8_t neg(uint8_t operand);
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register16_t m_d;
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register16_t m_x;
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register16_t m_y;
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register16_t m_u;
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register16_t m_s;
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uint8_t m_dp;
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uint8_t m_cc;
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PinLevel m_firq;
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};
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} |