This book is a guide to the 65c02 Assembly language. This book will teach the different memory addressing modes and instructions of the 8-bit WDC 65c02 processor.

This is an edit of the 6502 Assembly book, with the addition of the new instructions/modes on the 65c02.

Syntax edit

Syntax will vary between assemblers - this book will use the following syntax throughout:

Numerical representations
Syntax Base Example
%00001111 Binary LDA #%0001
$FA Hexadecimal LDA #$0E
123 Decimal LDA #100

Introduction edit

The 65C02 CPU has an 8-bit data bus, and a 16-bit address bus. All registers are 8-bit except for the 16-bit Program Counter (PC) register. Therefore the CPU is considered to be 8-bit.

That the address bus is 16-bit means that the CPU can access 2^16 individual bytes of memory, from address $0000 to address $FFFF, which is 65536 bytes (64KB).

Communication with peripheral units (e.g. video, audio, disk and controllers for a game system) is often performed with memory-mapped I/O.

The memory is divided into "pages", each of 256 bytes (within the range of an 8-bit offset). Page n is the n'th page in the memory, with a starting address of 256*n, and end address of (256*(n+1))-1. E.g. the "zero page" starts at address 0, and ends at address 255. See memory layout below for more details.

Slightly less than half of the 65c02 CPUs opcodes deal with memory stored in the Zero Page. Memory stored in the zero page often takes less time to process.

Registers edit

Registers
Register Size (bits) Purpose
Accumulator (A) 8 Used to perform calculations on data.
Instructions can operate directly on the accumulator instead of spending CPU cycles to access memory
X register (X) 8 Used as an index in some addressing modes
Y register (Y) 8 Used as an index in some addressing modes
Program Counter (PC) 16 Points to the address of the next instruction to be executed
Stack Pointer (SP) 8 Stores the stack index into which the next stack element will be inserted.
The address of this position is $0100 + SP. SP is initially set to $FD
Status (SR) 8 Each bit represents a status flag. Flags indicate the state of the CPU, or information about the result of the previous instruction.
See the table below for a description of each flag

Status Flags
Bit Symbol Name Description
7 N Negative

Compare: Set if the register's value is less than the input value
Otherwise: Set if the result was negative, i.e. bit 7 of the result was set

6 V Overflow

Arithmetic: Set if a signed overflow occurred during addition or subtraction, i.e. the sign of the result differs from the sign of both the input and the accumulator
BIT: Set to bit 6 of the input

5 - (Unused) Always set
4 B[1] Break Set if an interrupt request has been triggered by a BRK instruction
3 D Decimal Decimal mode[2]: mathematical instructions will treat the inputs and outputs as decimal numbers.
E.g. $09 + $01 = $10
2 I Interrupt Disable Disables interrupts while set
1 Z Zero

Compare: Set if the register's value is equal to the input value
BIT: Set if the result of logically ANDing the accumulator with the input results in 0
Otherwise: Set if result was zero

0 C Carry Carry/Borrow flag used in math and rotate operations

Arithmetic: Set if an unsigned overflow occurred during addition or subtraction, i.e. the result is less than the initial value (or equal to the initial value, if the carry flag was set going in)
Compare: Set if register's value is greater than or equal to the input value
Shifting: Set to the value of the eliminated bit of the input, i.e. bit 7 when shifting left, or bit 0 when shifting right

Memory layout edit

16-bit values are stored in memory in little-endian, so the least significant byte is stored before the most significant. E.g. if address $0000 contains $FF and address $0001 contains $00, reading a two-byte value from $0000 will result in $00FF.

Signed integers are in two's complement and can represent values from -128 (%10000000) to +127 (%01111111). Bit 7 is set if the integer is negative.

The 6502's program counter is 16 bits wide, so up to 2^16 (65536) bytes of memory are addressable. Certain regions of memory are reserved for particular purposes:

Memory regions
Region Contents Description
$0000 - $00FF Zero pageThe first page of memory, which is faster to access than other pages.
Instructions can specify addresses within the zero page with a single byte as opposed to two, so instructions that use the zero page instead of any other page require one less CPU cycle to execute
$0100 - $01FF StackLast-in first-out data structure. Grows backwards from $01FF to $0100.
Used by some transfer, stack, and subroutine instructions
$0200 - $FFFF General-purposeMemory that can be used for whatever purpose needed.
Devices that use the 6502 processor may choose to reserve sub-regions for other purposes, such as memory-mapped I/O

Memory Addressing Modes edit

Each instruction uses one of thirteen memory addressing modes, which determines the operand of the instruction. An example is provided for each.

Accumulator: A edit

The Accumulator is implied as the operand, so no address needs to be specified.

Example

Using the ASL (Arithmetic Shift Left) instruction with no operands, the Accumulator is always the value being shifted left.

ASL

Implied: i edit

The operand is implied, so it does not need to be specified.

Example

The operands being implied here are X, the source of the transfer, and A, the destination of the transfer.

TXA

Immediate: # edit

The operand is used directly to perform the computation.

Example

The value $22 is loaded into the Accumulator.

LDA #$22

Absolute: a edit

A full 16-bit address is specified and the byte at that address is used to perform the computation.

Example

The value at address $D010 is loaded into the X register.

LDX $D010

Zero Page: zp edit

A single byte specifies an address in the first page of memory ($00xx), also known as the zero page, and the byte at that address is used to perform the computation.

Example

The value at address $0002 is loaded into the Y register.

LDY $02

Stack: s edit

Essentially the same as Implied (i). The difference is that these instructions perform stack operations; pushing or pulling operands from the stack.

Relative: r edit

The offset specified is added to the current address stored in the Program Counter (PC). Offsets can range from -128 to +127.

Example

The offset $2D is added to the address in the Program Counter (say $C100). The destination of the branch (if taken) will be $C12D.

BPL $2D

Absolute Indirect: (a) edit

The little-endian two-byte value stored at the specified address is used to perform the computation. Only used by the JMP instruction.

Example

The addresses $A001 and $A002 are read, returning $FF and $00 respectively. The address $00FF is then jumped to.

JMP ($A001)

Absolute Indirect Indexed with X: (a,x) edit

The value in X is added to the specified address for a sum address. The little-endian address stored at the two-byte pair of sum address (LSB) and sum address plus one (MSB) is loaded and the value at that address is used to perform the computation. Only used by the JMP instruction.

Example

The value $06 in X is added to $EO15 for a sum of $EO1B. The address $D010 at addresses $E01B and $E01C are read. The address $D010 is then jumped to.

JMP ($E015,X)

Absolute Indexed with X: a,x edit

The value in X is added to the specified address for a sum address. The value at the sum address is used to perform the computation.

Example

The value $02 in X is added to $C001 for a sum of $C003. The value $5A at address $C003 is used to perform the add with carry (ADC) operation.

ADC $C001,X

Absolute Indexed with Y: a,y edit

The value in Y is added to the specified address for a sum address. The value at the sum address is used to perform the computation.

Example

The value $03 in Y is added to $F001 for a sum of $F004. The value $EF at address $F004 is incremented (INC) and $F0 is written back to $F004.

INC $F001,Y

Zero Page Indexed with X: zp,x edit

The value in X is added to the specified zero page address for a sum address. The value at the sum address is used to perform the computation.

Example

The value $02 in X is added to $01 for a sum of $03. The value $A5 at address $0003 is loaded into the Accumulator.

LDA $01,X

Zero Page Indexed with Y: zp,y edit

The value in Y is added to the specified zero page address for a sum address. The value at the sum address is used to perform the computation.

Example

The value $03 in Y is added to $01 for a sum of $04. The value $E3 at address $0004 is loaded into the Accumulator.

LDA $01,Y

Zero Page Indexed Indirect: (zp,x) edit

The value in X is added to the specified zero page address for a sum address. The little-endian address stored at the two-byte pair of sum address (LSB) and sum address plus one (MSB) is loaded and the value at that address is used to perform the computation.

Example

The value $02 in X is added to $15 for a sum of $17. The address $D010 at addresses $0017 and $0018 will be where the value $0F in the Accumulator is stored.

STA ($15,X)

Zero Page Indirect: (zp) edit

The little-endian address stored at the two-byte pair of zero page address (LSB) and zero page address plus one (MSB) is loaded and the value at that address is used to perform the computation.

Example

The address $D010 at addresses $0015 and $0016 will be where the value $0F in the Accumulator is stored.

STA ($15)

Zero Page Indirect Indexed with Y: (zp),y edit

The value in Y is added to the address at the little-endian address stored at the two-byte pair of the specified address (LSB) and the specified address plus one (MSB). The value at the sum address is used to perform the computation. Indeed addressing mode actually repeats exactly the Accumulator register's digits.

Example

The value $03 in Y is added to the address $C235 at addresses $002A and $002B for a sum of $C238. The Accumulator is then exclusive ORed with the value $2F at $C238.

EOR ($2A),Y

Instructions edit

These are the instructions for the 6502 processor including an ASCII visual, a list of affected flags, and a table of opcodes for acceptable addressing modes.

Load and Store edit

Load Accumulator with Memory: LDA    Load Index X with Memory: LDX    Load Index Y with Memory: LDY   

M -> A

Flags: N, Z

M -> X

Flags: N, Z

M -> Y

Flags: N, Z

Addressing Mode Opcode
a AD
a,x BD
a,y B9
# A9
zp A5
(zp,x) A1
(zp) B2
zp,x B5
(zp),y B1
Addressing Mode Opcode
a AE
a,y BE
# A2
zp A6
zp,y B6
Addressing Mode Opcode
a AC
a,x BC
# A0
zp A4
zp,x B4
Store Accumulator in Memory: STA    Store Index X in Memory: STX    Store Index Y in Memory: STY   

A -> M

Flags: none

X -> M

Flags: none

Y -> M

Flags: none

Addressing Mode Opcode
a 8D
a,x 9D
a,y 99
zp 85
(zp,x) 81
(zp) 92
zp,x 95
(zp),y 91
Addressing Mode Opcode
a 8E
zp 86
zp,y 96
Addressing Mode Opcode
a 8C
zp 84
zp,x 94
Store Zero in Memory: STZ   

0 -> M

Flags: none

Addressing Mode Opcode
a 9C
a,x 9E
zp 64
zp,x 74

Arithmetic edit

Add Memory to Accumulator with Carry: ADC    Subtract Memory from Accumulator with Borrow: SBC   

A + M + C -> A

Flags: N, V, Z, C

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) 72
zp,x 75
(zp),y 71
Addressing Mode Opcode
a ED
a,x FD
a,y F9
# E9
zp E5
(zp,x) E1
(zp) F2
zp,x F5
(zp),y F1

Increment and Decrement edit

Increment Memory by One: INC    Increment Index X by One: INX    Increment Index Y by One: INY   

M + 1 -> M

Flags: N, Z

X + 1 -> X

Flags: N, Z

Y + 1 -> Y

Flags: N, Z

Addressing Mode Opcode
a EE
a,x FE
zp E6
zp,x F6
A 1A
Addressing Mode Opcode
i E8
Addressing Mode Opcode
i C8
Decrement Memory by One: DEC    Decrement Index X by One: DEX    Decrement Index Y by One: DEY   

M - 1 -> M

Flags: N, Z

X - 1 -> X

Flags: N, Z

Y - 1 -> Y

Flags: N, Z

Addressing Mode Opcode
a CE
a,x DE
zp C6
zp,x D6
A 3A
Addressing Mode Opcode
i CA
Addressing Mode Opcode
i 88

Shift and Rotate edit

Arithmetic Shift Left One Bit: ASL    Logical Shift Right One Bit: LSR   

C <- 7 6 5 4 3 2 1 0 <- 0

Flags: N, Z, C

0 -> 7 6 5 4 3 2 1 0 -> C

Flags: N, Z, C

Addressing Mode Opcode
a 0E
a,x 1E
A 0A
zp 06
zp,x 16
Addressing Mode Opcode
a 4E
a,x 5E
A 4A
zp 46
zp,x 56
Rotate Left One Bit: ROL    Rotate Right One Bit: ROR   

C <- 7 6 5 4 3 2 1 0 <- C

Flags: N, Z, C

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
Addressing Mode Opcode
a 6E
a,x 7E
A 6A
zp 66
zp,x 76

Logic edit

AND Memory with Accumulator: AND    OR Memory with Accumulator: ORA    Exclusive-OR Memory with Accumulator: EOR   

A & M -> A

Flags: N, Z

A | M -> A

Flags: N, Z

A ^ M -> A

Flags: N, Z

Addressing Mode Opcode
a 2D
a,x 3D
a,y 39
# 29
zp 25
(zp,x) 21
(zp) 32
zp,x 35
(zp),y 31
Addressing Mode Opcode
a 0D
a,x 1D
a,y 19
# 09
zp 05
(zp,x) 01
(zp) 12
zp,x 15
(zp),y 11
Addressing Mode Opcode
a 4D
a,x 5D
a,y 59
# 49
zp 45
(zp,x) 41
(zp) 52
zp,x 55
(zp),y 51

Compare and Test Bit edit

The Negative (N), Zero (Z), and Carry (C) status flags are used for conditional (branch) instructions.

All Compare instructions affect flags in the same way:

Condition N Z C
Register < Memory 1 0 0
Register = Memory 0 1 1
Register > Memory 0 0 1
Compare Memory and Accumulator: CMP    Compare Memory and Index X: CPX    Compare Memory with Index Y: CPY   

A - M

Flags: N, Z, C

X - M

Flags: N, Z, C

Y - M

Flags: N, Z, C

Addressing Mode Opcode
a CD
a,x DD
a,y D9
# C9
zp C5
(zp,x) C1
(zp) D2
zp,x D5
(zp),y D1
Addressing Mode Opcode
a EC
# E0
zp E4
Addressing Mode Opcode
a CC
# C0
zp C4

Test Bits in Memory with Accumulator: BIT

A & M

Flags: N = M7, V = M6, Z

Addressing Mode Opcode
a 2C
a,x 3C
# 89
zp 24
zp,x 34

Branch edit

Branch unconditionally: BRA   

Branch if 1 = 1

Flags: none

Addressing Mode Opcode
r 80
Branch on Carry Clear: BCC    Branch on Carry Set: BCS   

Branch if C = 0

Flags: none

Branch if C = 1

Flags: none

Addressing Mode Opcode
r 90
Addressing Mode Opcode
r B0
Branch on Result not Zero: BNE    Branch on Result Zero: BEQ   

Branch if Z = 0

Flags: none

Branch if Z = 1

Flags: none

Addressing Mode Opcode
r D0
Addressing Mode Opcode
r F0
Branch on Result Plus: BPL    Branch on Result Minus: BMI   

Branch if N = 0

Flags: none

Branch if N = 1

Flags: none

Addressing Mode Opcode
r 10
Addressing Mode Opcode
r 30
Branch on Overflow Clear: BVC    Branch on Overflow Set: BVS   

Branch if V = 0

Flags: none

Branch if V = 1

Flags: none

Addressing Mode Opcode
r 50
Addressing Mode Opcode
r 70

Unlike the other branch instructions, BBR and BBS have two operands. The M operand, used for the Set or Reset comparison, is always the zp addressing mode. The branch address operand is the r addressing mode, and has the same meaning as the other branch instructions.

Branch on Bit Reset: BBR    Branch on Bit Set: BBS   
Branch if (M >> n) & 1 = 0

Flags: none

Branch if (M >> n) & 1 = 1

Flags: none

Bit Addressing Mode Opcode
BBR0 r 0F
BBR1 r 1F
BBR2 r 2F
BBR3 r 3F
BBR4 r 4F
BBR5 r 5F
BBR6 r 6F
BBR7 r 7F
Bit Addressing Mode Opcode
BBS0 r 8F
BBS1 r 9F
BBS2 r AF
BBS3 r BF
BBS4 r CF
BBS5 r DF
BBS6 r EF
BBS7 r FF

Transfer edit

Transfer Accumulator to Index X: TAX    Transfer Index X to Accumulator: TXA   

A -> X

Flags: N, Z

X -> A

Flags: N, Z

Addressing Mode Opcode
i AA
Addressing Mode Opcode
i 8A
Transfer Accumulator to Index Y: TAY    Transfer Index Y to Accumulator: TYA   

A -> Y

Flags: N, Z

Y -> A

Flags: N, Z

Addressing Mode Opcode
i A8
Addressing Mode Opcode
i 98
Transfer Stack Pointer to Index X: TSX    Transfer Index X to Stack Pointer: TXS   

S -> X

Flags: N, Z

X -> S

Flags: none

Addressing Mode Opcode
i BA
Addressing Mode Opcode
i 9A

Stack edit

Push Accumulator on Stack: PHA    Pull Accumulator from Stack: PLA   

A -> S

Flags: none

S -> A

Flags: N, Z

Addressing Mode Opcode
i 48
Addressing Mode Opcode
i 68
Push Index X on Stack: PHX    Pull Index X from Stack: PLX   

X -> S

Flags: none

S -> X

Flags: none

Addressing Mode Opcode
i DA
Addressing Mode Opcode
i FA
Push Index Y on Stack: PHY    Pull Index Y from Stack: PLY   

Y -> S

Flags: none

S -> Y

Flags: none

Addressing Mode Opcode
i 5A
Addressing Mode Opcode
i 7A
Push Processor Status on Stack: PHP    Pull Processor Status from Stack: PLP   

P -> S

Flags: none

S -> P

Flags: all

Addressing Mode Opcode
i 08
Addressing Mode Opcode
i 28

The processor status is stored as a single byte with the following flags bits from high to low: NV--DIZC.

Subroutines and Jump edit

Jump to New Location: JMP

Jump to new location by changing the value of the program counter.

Flags: none

Addressing Mode Opcode
a 4C
(a) 6C
(a,x) 7C

Jump to New Location Saving Return Address: JSR

Jumps to a subroutine

The address before the next instruction (PC - 1) is pushed onto the stack: first the upper byte followed by the lower byte. As the stack grows backwards, the return address is therefore stored as a little-endian number in memory.
PC is set to the target address.

Flags: none

Addressing Mode Opcode
a 20

Return from Subroutine: RTS

Return from a subroutine to the point where it called with JSR.

The return address is popped from the stack (low byte first, then high byte).
The return address is incremented and stored in PC.

Flags: none

Addressing Mode Opcode
i 60

Return from Interrupt: RTI

Return from an interrupt.

SR is popped from the stack.
PC is popped from the stack.

Flags: all

Addressing Mode Opcode
i 40

Set and Clear edit

Clear Carry Flag: CLC    Set Carry Flag: SEC   

0 -> C

Flags: C = 0

1 -> C

Flags: C = 1

Addressing Mode Opcode
i 18
Addressing Mode Opcode
i 38
Clear Decimal Mode: CLD    Set Decimal Mode: SED   

0 -> D

Flags: D = 0

1 -> D

Flags: D = 1

Addressing Mode Opcode
i D8
Addressing Mode Opcode
i F8
Clear Interrupt Disable Status: CLI    Set Interrupt Disable Status: SEI   

0 -> I

Flags: I = 0

1 -> I

Flags: I = 1

Addressing Mode Opcode
i 58
Addressing Mode Opcode
i 78
Clear Overflow Flag: CLV   

0 -> V

Flags: V = 0

Addressing Mode Opcode
i B8
Reset Memory Bit: RMB    Set Memory Bit: SMB   

M & ~(1 << n) -> M

Flags: none

Bit Addressing Mode Opcode
RMB0 zp 07
RMB1 zp 17
RMB2 zp 27
RMB3 zp 37
RMB4 zp 47
RMB5 zp 57
RMB6 zp 67
RMB7 zp 77

M | (1 << n) -> M

Flags: none

Bit Addressing Mode Opcode
SMB0 zp 87
SMB1 zp 97
SMB2 zp A7
SMB3 zp B7
SMB4 zp C7
SMB5 zp D7
SMB6 zp E7
SMB7 zp F7

Miscellaneous edit

Break: BRK   

Force an Interrupt.

This is a two-byte instruction, where the second byte is ignored by the processor. The 2nd byte can be used as argument to the interrupt service routine.

Flags: B = 1, I = 1

Addressing Mode Opcode
i 00

No Operation: NOP   

No Operation

Flags: none

Addressing Mode Opcode
i EA

Wait for Interrupt: WAI   

Wait for Interrupt

Flags: none

Addressing Mode Opcode
i CB

Stop mode: STP   

Stop mode

Flags: none

Addressing Mode Opcode
i DB

Opcode map edit

List of all the OpCodes present. An opcode is an "operation code", the first byte in an instruction. This byte decides which operation is being performed. Multiple assembler mnemonics (eg. ADC, BIT, JMP et.c.) correspond to several different opcodes. There is one opcode per addressing mode used. For example, the menmonic ASL have multiple opcodes, one for each addressing mode supported by the CPU.

Opcodes marked with an asterisk (*) are opcodes that did not exist for the 6502 CPU.

Blank entries are supposed to behave identical the NOP instruction (EA).

Instruction table
High nibble Low nibble
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00 BRK
s
ORA
(zp,x)
TSB
zp *
ORA
zp
ASL
zp
RMB0
zp *
PHP
s
ORA
#
ASL
A
TSB
a *
ORA
a
ASL
a
BBR0
r *
10 BPL
r
ORA
(zp),y
ORA
(zp) *
TRB
zp *
ORA
zp,x
ASL
zp,x
RMB1
zp *
CLC
i
ORA
a,y
INC
A *
TRB
a *
ORA
a,x
ASL
a,x
BBR1
r *
20 JSR
a
AND
(zp,x)
BIT
zp
AND
zp
ROL
zp
RMB2
zp *
PLP
s
AND
#
ROL
A
BIT
a
AND
a
ROL
a
BBR2
r *
30 BMI
r
AND
(zp),y
AND
(zp) *
BIT
zp,x
AND
zp,x
ROL
zp,x
RMB3
zp *
SEC
i
AND
a,y
DEC
A *
BIT
a,x *
AND
a,x
ROL
a,x
BBR3
r *
40 RTI
s
EOR
(zp,x)
EOR
zp
LSR
zp
RMB4
zp *
PHA
s
EOR
#
LSR
A
JMP
a
EOR
a
LSR
a
BBR4
r *
50 BVC
r
EOR
(zp),y
EOR
(zp) *
EOR
zp,x
LSR
zp,x
RMB5
zp *
CLI
i
EOR
a,y
PHY
s *
EOR
a,x
LSR
a,x
BBR5
r *
60 RTS
s
ADC
(zp,x)
STZ
zp
ADC
zp
ROR
zp
RMB6
zp *
PLA
s
ADC
#
ROR
A
JMP
(a)
ADC
a
ROR
a
BBR6
r *
70 BVS
r
ADC
(zp),y
ADC
(zp) *
STZ
zp,x
ADC
zp,x
ROR
zp,x
RMB7
zp *
SEI
i
ADC
a,y
PLY
s *
JMP
(a,x) *
ADC
a,x
ROR
a,x
BBR7
r *
80 BRA
r *
STA
(zp,x)
STY
zp
STA
zp
STX
zp
SMB0
zp *
DEY
i
BIT
# *
TXA
i
STY
a
STA
a
STX
a
BBS0
r *
90 BCC
r
STA
(zp),y
STA
(zp) *
STY
zp,x
STA
zp,x
STX
zp,y
SMB1
zp *
TYA
i
STA
a,y
TXS
i
STZ
a *
STA
a,x
STZ
a,x *
BBS1
r *
A0 LDY
#
LDA
(zp,x)
LDX
#
LDY
zp
LDA
zp
LDX
zp
SMB2
zp *
TAY
i
LDA
#
TAX
i
LDY
a
LDA
a
LDX
a
BBS2
r *
B0 BCS
r
LDA
(zp),y
LDA
(zp) *
LDY
zp,x
LDA
zp,x
LDX
zp,y
SMB3
zp *
CLV
i
LDA
a,y
TSX
i
LDY
a,x
LDA
a,x
LDX
a,y
BBS3
r *
C0 CPY
#
CMP
(zp,x)
CPY
zp
CMP
zp
DEC
zp
SMB4
zp *
INY
i
CMP
#
DEX
i
WAI
i *
CPY
a
CMP
a
DEC
a
BBS4
r *
D0 BNE
r
CMP
(zp),y
CMP
(zp) *
CMP
zp,x
DEC
zp,x
SMB5
zp *
CLD
i
CMP
a,y
PHX
s *
STP
i *
CMP
a,x
DEC
a,x
BBS5
r *
E0 CPX
#
SBC
(zp,x)
CPX
zp
SBC
zp
INC
zp
SMB6
zp *
INX
i
SBC
#
NOP
i
CPX
a
SBC
a
INC
a
BBS6
r *
F0 BEQ
r
SBC
(zp),y
SBC
(zp) *
SBC
zp,x
INC
zp,x
SMB7
zp *
SED
i
SBC
a,y
PLX
s *
SBC
a,x
INC
a,x
BBS7
r *

References edit

  1. [1], The B flag does not represent an actual CPU register

Further reading edit