Apple I Replica Creation -- Appendix D: Instructions by Category
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Appendix D |
Load and Store
LDA — Load Accumulator with Memory
M → A
Flags: N, Z
| Addressing Mode | Opcode |
| a | AD |
| a,x | BD |
| a,y | B9 |
| # | A9 |
| zp | A5 |
| (zp,x) | A1 |
| zp,x | B5 |
| (zp),y | B1 |
LDX — Load Index X with Memory
M → X
Flags: N, Z
| Addressing Mode | Opcode |
| a | AE |
| a,y | BE |
| # | A2 |
| zp | A6 |
| zp,y | B6 |
LDY — Load Index Y with Memory
M → Y
Flags: N, Z
| Addressing Mode | Opcode |
| a | AC |
| a,x | BC |
| # | A0 |
| zp | A4 |
| zp.x | B4 |
STA — Store Accumulator in Memory
A → M
Flags: none
| Addressing Mode | Opcode |
| a | 8D |
| a,x | 9D |
| a,y | 99 |
| zp | 85 |
| (zp,x) | 81 |
| zp,x | 95 |
| (zp),y | 91 |
STX — Store Index X in Memory
X → M
Flags: none
| Addressing Mode | Opcode |
| a | 8E |
| zp | 86 |
| zp,y | 96 |
STY — Store Index Y in Memory
Y → M
Flags: none
| Addressing Mode | Opcode |
| a | 8C |
| zp | 84 |
| zp,x | 94 |
Arithmetic
ADC — Add Memory to Accumulator with Carry
A + M + C → A
Flags: N, V, Z, C,
| Addressing Mode | Opcode |
| a | 6D |
| a,x | 7D |
| a,y | 79 |
| # | 69 |
| zp | 65 |
| (zp,x) | 61 |
| zp,x | 75 |
| (zp),y | 71 |
SBC — Subtract Memory from Accumulator with Borrow
A — M - ~C → A
Flags: N, V, Z, C
| Addressing Mode | Opcode |
| a | ED |
| a,x | FD |
| a,y | F9 |
| # | E9 |
| zp | E5 |
| (zp,x) | E1 |
| zp,x | F5 |
| (zp),y | F1 |
Increment and Decrement
INC — Increment Memory by One
M + 1 → M
Flags: N, Z
| Addressing Mode | Opcode |
| a | EE |
| a,x | FE |
| zp | E6 |
| zp,x | F6 |
INX — Increment Index X by One
X + 1 → X
Flags: N, Z
| Addressing Mode | Opcode |
| i | E8 |
INY — Increment Index Y by One
Y + 1 → Y
Flags: N, Z
| Addressing Mode | Opcode |
| i | C8 |
DEC — Decrement Memory by One
M — 1 → M
Flags: N, Z
| Addressing Mode | Opcode |
| a | CE |
| a,x | DE |
| zp | C6 |
| zp,x | D6 |
DEX — Decrement Index X by One
X — 1 → X
Flags: N, Z
| Addressing Mode | Opcode |
| i | CA |
DEY — Decrement Index Y by One
Y — 1 → Y
Flags: N, Z
| Addressing Mode | Opcode |
| i | 88 |
Shift and Rotate
ASL — Accumulator Shift Left One Bit
C ← 7 6 5 4 3 2 1 0 ← 0
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | 0E |
| a,x | 1E |
| A | 0A |
| zp | 06 |
| zp.x | 16 |
LSR — Logical Shift Right One Bit
0 → 7 6 5 4 3 2 1 0 → C
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | 4E |
| a,x | 5E |
| A | 4A |
| zp | 46 |
| zp.x | 56 |
ROL — Rotate Left One Bit
C ← 7 6 5 4 3 2 1 0 ← C
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | 2E |
| a,x | 3E |
| A | 2A |
| zp | 26 |
| zp.x | 36 |
ROR — Rotate Right One Bit
C → 7 6 5 4 3 2 1 0 → C
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | 6E |
| a,x | 7E |
| A | 6A |
| zp | 66 |
| zp.x | 76 |
Logic
AND — AND Memory with Accumulator
A ^ M → A
Flags: N, Z
| Addressing Mode | Opcode |
| a | 2D |
| a,x | 3D |
| a,y | 39 |
| # | 29 |
| zp | 25 |
| (zp,x) | 21 |
| zp,x | 35 |
| (zp),y | 31 |
ORA — OR Memory with Accumulator
A v M → A
Flags: N, Z
| Addressing Mode | Opcode |
| a | 0D |
| a,x | 1D |
| a,y | 19 |
| # | 09 |
| zp | 05 |
| (zp,x) | 01 |
| zp,x | 15 |
| (zp),y | 11 |
EOR — Exclusive-OR Memory with Accumulator
A v M → A
Flags: N, Z
| Addressing Mode | Opcode |
| a | 4D |
| a,x | 5D |
| a,y | 59 |
| # | 49 |
| zp | 45 |
| (zp,x) | 41 |
| zp,x | 55 |
| (zp),y | 51 |
Compare and Test Bit
For all Compare instructions:
| Condition | N | Z | C |
| Register < Memory | 1 | 0 | 0 |
| Register = Memory | 0 | 1 | 1 |
| Register > Memory | 0 | 0 | 1 |
CMP — Compare Memory and Accumulator
A - M
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | CD |
| a,x | DD |
| a,y | D9 |
| # | C9 |
| zp | C5 |
| (zp,x) | C1 |
| zp,x | D5 |
| (zp),y | D1 |
CPX — Compare Memory and Index X
X - M
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | EC |
| # | E0 |
| zp | E4 |
CPY — Compare Memory and Index Y
Y - M
Flags: N, Z, C
| Addressing Mode | Opcode |
| a | CC |
| # | C0 |
| zp | C4 |
BIT — Test Bits in Memory with Accumulator
A ^ M
Flags: N = M7, V = M6, Z
| Addressing Mode | Opcode |
| a | 2C |
| # | 89 |
| zp | 24 |
Branch
BCC — Branch on Carry Clear
Branch if C = 0
Flags: none
| Addressing Mode | Opcode |
| r | 90 |
BCS — Branch on Carry Set
Branch if C = 1
Flags: none
| Addressing Mode | Opcode |
| r | B0 |
BEQ — Branch on Result Zero
Branch if Z = 1
Flags: none
| Addressing Mode | Opcode |
| r | F0 |
BMI — Branch on Result Minus
Branch if N = 1
Flags: none
| Addressing Mode | Opcode |
| r | 30 |
BNE — Branch on Result Not Zero
Branch if Z = 0
Flags: none
| Addressing Mode | Opcode |
| r | D0 |
BPL — Branch on Result Plus
Branch if N = 0
Flags: none
| Addressing Mode | Opcode |
| r | 10 |
BVC — Branch on Overflow Clear
Branch if V = 0
Flags: none
| Addressing Mode | Opcode |
| r | 50 |
BVS — Branch on Overflow Set
Branch if V = 1
Flags: none
| Addressing Mode | Opcode |
| r | 70 |
Transfer
TAX — Transfer Accumulator to Index X
A → X
Flags: N, Z
| Addressing Mode | Opcode |
| i | AA |
TXA — Transfer Index X to Accumulator
X → A
Flags: N, Z
| Addressing Mode | Opcode |
| i | 8A |
TAY — Transfer Accumulator to Index Y
A → Y
Flags: N, Z
| Addressing Mode | Opcode |
| i | AB |
TYA — Transfer Index Y to Accumulator
Y → A
Flags: N, Z
| Addressing Mode | Opcode |
| i | 98 |
TSX — Transfer Stack Pointer to Index X
S → X
Flags: N, Z
| Addressing Mode | Opcode |
| i | BA |
TXS — Transfer Index X to Stack Register
X → S
Flags: N, Z
| Addressing Mode | Opcode |
| i | 9A |
Stack
PHA — Push Accumulator on Stack
A → S
Flags: none
| Addressing Mode | Opcode |
| i | 48 |
PLA — Pull Accumulator from Stack
S → A
Flags: N, Z
| Addressing Mode | Opcode |
| i | 68 |
PHP — Push Processor Status on Stack
P → S
Flags: none
| Addressing Mode | Opcode |
| i | 08 |
PLP — Pull Processor Status from Stack
S → P
Flags: all
| Addressing Mode | Opcode |
| i | 28 |
Subroutines and Jump
JMP — Jump to New Location
Jump to new location
Flags: none
| Addressing Mode | Opcode |
| a | 4C |
| (a,x) | 7C |
| (a) | 6C |
JSR — Jump to New Location Saving Return Address
Jump to Subroutine
Flags: none
| Addressing Mode | Opcode |
| a | 20 |
RTS — Return from Subroutine
Return from Subroutine
Flags: none
| Addressing Mode | Opcode |
| i | 60 |
RTI — Return from Interrupt
Return from Interrupt
Flags: none
| Addressing Mode | Opcode |
| i | 40 |
Set and Clear
SEC — Set Carry Flag
1 → C
Flags: none
| Addressing Mode | Opcode |
| i | 38 |
SED — Set Decimal Mode
1 → D
Flags: none
| Addressing Mode | Opcode |
| i | F8 |
SEI — Set Interrupt Disable Status
1 → I
Flags: none
| Addressing Mode | Opcode |
| i | 78 |
CLC — Clear Carry Flag
0 → C
Flags: C = 0
| Addressing Mode | Opcode |
| i | 18 |
CLD — Clear Decimal Mode
0 → D
Flags: D = 0
| Addressing Mode | Opcode |
| i | D8 |
CLI — Clear Interrupt Disable Bit
0 → I
Flags: I = 0
| Addressing Mode | Opcode |
| i | 58 |
CLV — Clear Overflow Flag
0 → V
Flags: V = 0
| Addressing Mode | Opcode |
| i | B8 |
Miscellaneous
NOP — No Operation
No Operation
Flags: none
| Addressing Mode | Opcode |
| i | EA |
BRK — Break
Force an interrupt
Flags: B = 1, I = 1
| Addressing Mode | Opcode |
| i | 00 |
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