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978ad1faaf
But weird forms. In most cases they basically are NOPs, except with different opcodes. In other cases, we call them NP2 and NP3s, and do so because they consume 2 or 3 bytes respectively (vs. just 1 with NOP). We had to teach some arcane magic to the emulator for this to work. We may want to refactor to decouple the number of bytes consumed from the address mode.
141 lines
4.4 KiB
C
141 lines
4.4 KiB
C
/*
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* mos6502.enums.h
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* Enums and other symbols for use with the mos 6502
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*
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* We have separated the definitions of address mode types, instruction
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* types, etc. into their own file so that we can include it in our main
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* source file, as well as from our unit test suite, without necessarily
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* adding them to the global namespace throughout the application.
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*/
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#ifndef _MOS6502_ENUMS_H_
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#define _MOS6502_ENUMS_H_
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/*
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* This defines all of the flags that are possible within the status (P)
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* register. Note that there is intentionally _no_ definition for the
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* 6th bit.
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*/
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enum status_flags {
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MOS_CARRY = 1,
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MOS_ZERO = 2,
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MOS_INTERRUPT = 4,
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MOS_DECIMAL = 8,
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MOS_BREAK = 16,
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MOS_OVERFLOW = 64,
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MOS_NEGATIVE = 128,
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};
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#define MOS_NVZ (MOS_NEGATIVE | MOS_OVERFLOW | MOS_ZERO)
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#define MOS_NVZC (MOS_NEGATIVE | MOS_OVERFLOW | MOS_ZERO | MOS_CARRY)
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#define MOS_NZ (MOS_NEGATIVE | MOS_ZERO)
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#define MOS_NZC (MOS_NEGATIVE | MOS_ZERO | MOS_CARRY)
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#define MOS_ZC (MOS_ZERO | MOS_CARRY)
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#define MOS_STATUS_DEFAULT (MOS_NEGATIVE | MOS_OVERFLOW | \
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MOS_INTERRUPT | MOS_ZERO | MOS_CARRY)
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/*
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* Here we define the various address modes that are possible. These do
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* not map to any significant numbers that are documented for the 6502
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* processor; the position of these symbols don't really matter, and are
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* generally (except for `NOA`, no address mode) in alphabetical order.
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*/
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enum addr_mode {
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NOA, // no address mode
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ACC, // accumulator
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ABS, // absolute
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ABX, // absolute x-index
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ABY, // absolute y-index
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BY2, // Consume 2 bytes (for NP2)
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BY3, // Consume 3 bytes (for NP3)
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IMM, // immediate
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IMP, // implied
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IND, // indirect
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IDX, // x-index indirect
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IDY, // indirect y-index
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REL, // relative
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ZPG, // zero page
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ZPX, // zero page x-index
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ZPY, // zero page y-index
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};
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/*
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* These define the various instructions as enum symbols; again, like
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* for address modes, the values of these enums are not actually
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* significant to the 6502 processor, and are only useful to we, the
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* programmers.
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*/
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enum instruction {
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ADC, // ADd with Carry
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AND, // bitwise AND
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ASL, // Arithmetic Shift Left
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BAD, // bad instruction
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BCC, // Branch on Carry Clear
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BCS, // Branch on Carry Set
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BEQ, // Branch on EQual to zero
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BIT, // BIT test
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BIM, // BIt test (imMediate mode) (* not a real instruction in the processor; just used by us)
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BMI, // Branch on MInus
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BNE, // Branch on Not Equal to zero
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BPL, // Branch on PLus
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BRA, // BRanch Always
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BRK, // BReaK (interrupt)
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BVC, // Branch on oVerflow Clear
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BVS, // Branch on oVerflow Set
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CLC, // CLear Carry
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CLD, // CLear Decimal
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CLI, // CLear Interrupt disable
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CLV, // CLear oVerflow
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CMP, // CoMPare
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CPX, // ComPare with X register
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CPY, // ComPare with Y register
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DEC, // DECrement
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DEX, // DEcrement X
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DEY, // DEcrement Y
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EOR, // Exclusive OR
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INC, // INCrement
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INX, // INcrement X
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INY, // INcrement Y
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JMP, // JuMP
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JSR, // Jump to SubRoutine
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LDA, // LoaD Accumulator
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LDX, // LoaD X
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LDY, // LoaD Y
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LSR, // Logical Shift Right
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NOP, // NO oPeration
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NP2, // No oPeration (2 bytes consumed)
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NP3, // No oPeration (3 bytes consumed)
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ORA, // OR with Accumulator
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PHA, // PusH Accumulator
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PHP, // PusH Predicate register
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PHX, // PusH X register
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PHY, // PusH Y register
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PLA, // PulL Accumulator
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PLP, // PulL Predicate register
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PLX, // PulL X register
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PLY, // PulL Y register
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ROL, // ROtate Left
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ROR, // ROtate Right
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RTI, // ReTurn from Interrupt
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RTS, // ReTurn from Subroutine
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SBC, // SuBtract with Carry
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SEC, // SEt Carry
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SED, // SEt Decimal
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SEI, // SEt Interrupt disable
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STA, // STore Accumulator
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STX, // STore X
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STY, // STore Y
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STZ, // STore Zero
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TAX, // Transfer Accumulator to X
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TAY, // Transfer Accumulator to Y
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TRB, // Test and Reset Bits
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TSB, // Test and Set Bits
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TSX, // Transfer Stack register to X
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TXA, // Transfer X to Accumulator
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TXS, // Transfer X to Stack register
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TYA, // Transfer Y to Accumulator
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};
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#endif
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