[PDF] Advanced 6502 Assembly Language Programming on the Apple //e





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AdvancedAssembly

Programming

for theApple IIStephen A. Edwards

6502 image fromhttps://www.pagetable.com/?p=1295

6502 image fromhttps://www.pagetable.com/?p=1295

DATA BUSADDR.

ADDRESS BUS

6502

4021222324252627282930313233343536373839

1201918171615141312111098765432

V SS

A12A13A14A15D7D6D5D4D3D2D1D0

(IN) SO V SS

A11A10A9A8A7A6A5A4A3A2A1A0V

CC

SYNCRDY

(OUT)

1IRQNMI

R/W 02 (OUT)

RESAfter Bill Bertram, Wikipedia

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

The 6502 Programmer"s Model

07

AACCUMULATOR

YINDEX REGISTERXINDEX REGISTER

15

PCLPCHPROGRAM COUNTER

S1STACK POINTER

STATUS REGISTERC

CarryZ

ZeroI

Interrupt DisableD

Decimal ModeB

BreakV

OverflowN

Negative

Source: Visual6502.org

Source: Visual6502.org

Source: Visual6502.org

6502 Instruction Encoding

groupmodeopcode groupmodeopcodeliteral or address groupmodeopcodelow address bytehigh address byte

6502 Instruction Encoding

10modeopcode"Group one" add, compare; most addressing modes

01modeopcode"Group two" shift/rotate, load/store X; fewer modes

001modeopcodeLoad/store Y, compare X & Y

0xy01op1Index register instructions

00011flagFlag set/clear

00001vflagBranches

0op0op000Stack instructions

11Unused in the 6502

6502 Instruction Encoding

10modeopcode"Group one" add, compare; most addressing modes

01modeopcode"Group two" shift/rotate, load/store X; fewer modes

001modeopcodeLoad/store Y, compare X & Y

0xy01op1Index register instructions

00011flagFlag set/clear

00001vflagBranches

0op0op000Stack instructions

11Unused in the 6502

6502 Instruction Encoding

10modeopcode"Group one" add, compare; most addressing modes

01modeopcode"Group two" shift/rotate, load/store X; fewer modes

001modeopcodeLoad/store Y, compare X & Y

0xy01op1Index register instructions

00011flagFlag set/clear

00001vflagBranches

0op0op000Stack instructions

11Unused in the 6502

6502 Instruction Encoding

10modeopcode"Group one" add, compare; most addressing modes

01modeopcode"Group two" shift/rotate, load/store X; fewer modes

001modeopcodeLoad/store Y, compare X & Y

0xy01op1Index register instructions

00011flagFlag set/clear

00001vflagBranches

0op0op000Stack instructions

11Unused in the 6502

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate A9LDA

A#$42 42

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate A9LDA

A#$42 42

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 42STA$42 42
$42Zero Page

Memory

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 42STA$42 42
$42Zero Page

MemoryA

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X $42,XADC

CZero Page

Memory$42,X

42
A

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X $42,XADC

C$42,X

42
AX+ $42 + XZero Page

Memory

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute EDSBC

Memory$4201

0142
A C

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute EDSBC

$4201Memory$4201 0142
A C

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X DDCMP

Memory$4205

0542
A N Z C

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X DDCMP

$4205 + XMemory$4205 0542
A

N Z CX+

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 39AND

Memory$4206,Y

0642
AAND

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 39AND

Y $4206 + YMemory+$4206,Y 0642
AAND

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 11 42ORA($42),Y; LogicalOR Indirect Indexed 11ORA

OR($42),Y

42

AMemory

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 11 42ORA($42),Y; LogicalOR Indirect Indexed 11ORA

$42 $43Zero Page

MemoryOR($42),Y

42

AMemory

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 11 42ORA($42),Y; LogicalOR Indirect Indexed 11ORA

$42 $43Zero Page

MemoryOR($42),Y

42
AY +Memory

Group One Instructions10modeopcode

A9 42LDA#$42; LoadAccumulator Immediate 85 42STA$42; StoreAccumulator Zero Page 75 42ADC$42,X; Addwith Carry Zero Page Indexed by X ED 01 42SBC$4201; Subtractw /CarryAbsolute DD 05 42CMP$4205,X; CompareAbsolute Indexed by X 39 06 42AND$4206,Y; LogicalAND Absolute Indexed by Y 11 42ORA($42),Y; LogicalOR Indirect Indexed 41 42EOR($42,X); ExclusiveOR Indexed Indirect 41EOR

Memory($42,X)

42
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