EightBit/MC6809/inc/mc6809.h
Adrian Conlon aa1a461db7 Whoops: missed a couple bad type conversions in the 6809 processor
Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
2018-08-20 22:20:24 +01:00

202 lines
5.8 KiB
C++

#pragma once
// Uses some information from:
// http://www.cpu-world.com/Arch/6809.html
#include <cstdint>
#include <Bus.h>
#include <BigEndianProcessor.h>
namespace EightBit {
class mc6809 : public BigEndianProcessor {
public:
enum StatusBits {
// Entire flag: set if the complete machine state was saved in the stack.
// If this bit is not set then only program counter and condition code
// registers were saved in the stack. This bit is used by interrupt
// handling routines only.
// The bit is cleared by fast interrupts, and set by all other interrupts.
EF = Bit7,
// Fast interrupt mask: set if the FIRQ interrupt is disabled.
FF = Bit6,
// Half carry: set if there was a carry from bit 3 to bit 4 of the result
// during the last add operation.
HF = Bit5,
// Interrupt mask: set if the IRQ interrupt is disabled.
IF = Bit4,
// Negative: set if the most significant bit of the result is set.
// This bit can be set not only by arithmetic and logical operations,
// but also by load / store operations.
NF = Bit3,
// Zero: set if the result is zero. Like the N bit, this bit can be
// set not only by arithmetic and logical operations, but also
// by load / store operations.
ZF = Bit2,
// Overflow: set if there was an overflow during last result calculation.
// Logical, load and store operations clear this bit.
VF = Bit1,
// Carry: set if there was a carry from the bit 7 during last add
// operation, or if there was a borrow from last subtract operation,
// or if bit 7 of the A register was set during last MUL operation.
CF = Bit0,
};
mc6809(Bus& bus);
Signal<mc6809> ExecutingInstruction;
Signal<mc6809> ExecutedInstruction;
virtual int execute(uint8_t opcode) final;
virtual int step() final;
virtual void powerOn() final;
register16_t& D() { return m_d; }
uint8_t& A() { return D().high; }
uint8_t& B() { return D().low; }
register16_t& X() { return m_x; }
register16_t& Y() { return m_y; }
register16_t& U() { return m_u; }
register16_t& S() { return m_s; }
uint8_t& DP() { return m_dp; }
uint8_t& CC() { return m_cc; }
PinLevel& IRQ() { return INT(); }
PinLevel& FIRQ() { return m_firq; }
protected:
virtual void reset() final;
private:
const uint8_t RESETvector = 0xfe; // RESET vector
const uint8_t NMIvector = 0xfc; // NMI vector
const uint8_t SWIvector = 0xfa; // SWI vector
const uint8_t IRQvector = 0xf8; // IRQ vector
const uint8_t FIRQvector = 0xf6; // FIRQ vector
const uint8_t SWI2vector = 0xf4; // SWI2 vector
const uint8_t SWI3vector = 0xf2; // SWI3 vector
const uint8_t RESERVEDvector = 0xf0; // RESERVED vector
// Execution helpers
int executeUnprefixed(uint8_t opcode);
int execute10(uint8_t opcode);
int execute11(uint8_t opcode);
// Register selection for "indexed"
register16_t& RR(int which);
// Addressing modes
void Address_direct(); // DP + fetched offset
void Address_indexed(); // Indexed address, complicated!
void Address_extended(); // Fetched address
// Addressing mode readers
// Single byte readers
uint8_t AM_immediate_byte();
uint8_t AM_direct_byte();
uint8_t AM_indexed_byte();
uint8_t AM_extended_byte();
// Word readers
register16_t AM_immediate_word();
register16_t AM_direct_word();
register16_t AM_indexed_word();
register16_t AM_extended_word();
// Flag adjustment
template<class T> void adjustZero(T datum) { clearFlag(CC(), ZF, datum); }
void adjustNegative(uint8_t datum) { setFlag(CC(), NF, datum & Bit7); }
void adjustNegative(uint16_t datum) { setFlag(CC(), NF, datum & Bit15); }
template<class T> void adjustNZ(T datum) {
adjustZero(datum);
adjustNegative(datum);
}
void adjustCarry(uint16_t datum) { setFlag(CC(), CF, datum & Bit8); } // 8-bit addition
void adjustCarry(uint32_t datum) { setFlag(CC(), CF, datum & Bit16); } // 16-bit addition
void adjustBorrow(uint16_t datum) { clearFlag(CC(), CF, datum & Bit8); } // 8-bit subtraction
void adjustBorrow(uint32_t datum) { clearFlag(CC(), CF, datum & Bit16); } // 16-bit subtraction
void adjustOverflow(uint8_t before, uint8_t data, uint8_t after) {
setFlag(CC(), VF, (before ^ data) & (before ^ after) & Bit7);
}
void adjustOverflow(uint16_t before, uint16_t data, uint16_t after) {
setFlag(CC(), VF, (before ^ data) & (before ^ after) & Bit15);
}
void adjustAddition(uint8_t before, uint8_t data, register16_t after) {
const auto result = after.low;
adjustNZ(result);
adjustCarry(after.word);
adjustOverflow(before, data, result);
}
void adjustAddition(uint16_t before, uint16_t data, uint32_t after) {
const register16_t result = after & Mask16;
adjustNZ(result.word);
adjustCarry(after);
adjustOverflow(before, data, result.word);
}
void adjustSubtraction(uint8_t before, uint8_t data, register16_t after) {
const auto result = after.low;
adjustNZ(result);
adjustBorrow(after.word);
adjustOverflow(before, data, result);
}
void adjustSubtraction(uint16_t before, uint16_t data, uint32_t after) {
const register16_t result = after & Mask16;
adjustNZ(result.word);
adjustBorrow(after);
adjustOverflow(before, data, result.word);
}
// Instruction implementations
void abx();
uint8_t adc(uint8_t operand, uint8_t data);
uint8_t add(uint8_t operand, uint8_t data, int carry = 0);
register16_t add(register16_t operand, register16_t data);
uint8_t andr(uint8_t operand, uint8_t data);
uint8_t asl(uint8_t operand);
uint8_t asr(uint8_t operand);
uint8_t clr();
void cmp(uint8_t operand, uint8_t data);
void cmp(register16_t operand, register16_t data);
uint8_t neg(uint8_t operand);
register16_t m_d;
register16_t m_x;
register16_t m_y;
register16_t m_u;
register16_t m_s;
uint8_t m_dp;
uint8_t m_cc;
PinLevel m_firq;
bool m_prefix10 = false;
bool m_prefix11 = false;
};
}