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

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

6502 image from https://www pagetable com/?p=1295 “Group two” shift/rotate, load/store X; fewer modes 5E 80 42 LSR $4280,X ;Logical Shift Right

[PDF] The 6502 Instruction Set

6502-Conj-de-Instrucoes doc 1 © Kevin Wilson The 6502 Arithmetic Shift Left N,Z,C LSR Logical Shift Right N,Z,C ROL Rotate Left N,Z,C ROR Rotate 

[PDF] 6502 Instant Reference Card - Atarimania

2 Arithmetic shift left Zero Page LDY nn,X Load Y ASL A Arithmetic shift left Accumulator LSR nn Logical shift right ASL n,X Arithmetic shift left Zero Page X

[PDF] Micro Logic 6502 Quick Reference Cardpdf - Apple Asimov

6502 (65XX) MICRO CHART **2 bytes must not cross page boundary 6502 Pins M A, Y, X, S, P = 1 byte Only PC is 2 bytes O 3 Logical shift right BEQ n

[PDF] Synertek Programming manual - 6502org

"All Rights Reserved" -- SYNERTEK CHAPTER 2 THE DATA BUS, ACCUMULATOR AND ARITHMETIC UNIT LSR--Logical Shift Right 148

[PDF] Programming the 6502, Rodney zaks - Retro Computing

The arithmetic logical unit (ALU) appears on the right of the il lustration The two numbers, correctly shifted, are then added and the sum is 276 This is simple

Appendix 1: 6502 Instruction Set

ing how arithmetic may be performed upon such numbers The number just after the point: that is, move it right or left until all digits to the left of the point a time and shift them accordingly, and this can also generate interrupts In the BBC  

5 The Registers

To enable the 6502 (65C02) to carry out its various operations, it contains arithmetic and logical operations are carried out through it Logical shift right

[PDF] 6502 Introduction

18 sept 2019 · Computer Systems Fundamentals: 6502 Introduction Shift and rotate, e g , 00001111 → 00011110 LSR (Logical Shift Right) use carry bit

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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
XORA

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

X+ $42 + X $43 + XZero Page

MemoryMemory($42,X)

42
XORA

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

X+ $42 + X $43 + XZero Page

MemoryMemory($42,X)

42
XORA

Apple II Zero

Page UsageMonitorApplesoftDOS 3.3ProDOS

Source: comp.sys.apple2 FAQ, Wagner,

Wirth and Lechner0

01 12 23
34
45
56
67
78
89
9A AB BC CD DE EF F

Apple II Zero

Page UsageMonitorApplesoftDOS 3.3ProDOS

Source: comp.sys.apple2 FAQ, Wagner,

Wirth and Lechner0

01 12 23
34
45
56
67
78
89
9A AB BC CD DE EF F

Apple II Zero

Page UsageMonitorApplesoftDOS 3.3ProDOS

Source: comp.sys.apple2 FAQ, Wagner,

Wirth and Lechner0

01 12 23
34
45
56
67
78
89
9A AB BC CD DE EF F

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate A2LDX

X#$42 42

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page 86STX$42 42

X$42Zero Page

Memory

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X F6INC

1$42,X

42
$42 + XZero Page

MemoryX+

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X CE 77 42DEC$4277; DecrementAbsolute CEDEC

1$4277

7742
$4277Memory

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X CE 77 42DEC$4277; DecrementAbsolute 0AASL;ArithmeticShift Left Accumulator 0AASL

0C

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X CE 77 42DEC$4277; DecrementAbsolute 0AASL;ArithmeticShift Left Accumulator 5E 80 42LSR$4280,X; LogicalShift Right Absolute Indexed by X 5ELSR$4280,X

8042
0C

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X CE 77 42DEC$4277; DecrementAbsolute 0AASL;ArithmeticShift Left Accumulator 5E 80 42LSR$4280,X; LogicalShift Right Absolute Indexed by X 2AROL;RotateLeft Accumulator 2AROL

C

Group Two Instructions01modeopcode

A2 42LDX#$42; LoadX Immediate 86 42STX$42; StoreX Zero Page F6 42INC$42,X; IncrementZero Page Indexed by X CE 77 42DEC$4277; DecrementAbsolute 0AASL;ArithmeticShift Left Accumulator 5E 80 42LSR$4280,X; LogicalShift Right Absolute Indexed by X 2AROL;RotateLeft Accumulator 6AROR;RotateRight Accumulator 6AROR

C

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 4CJMP$4240

4042

PCHPCL

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 6C 41 42JMP($4241); JumpIndirect 6CJMP$4241

4142

PCHPCL

$4241 $4242Memory

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 6C 41 42JMP($4241); JumpIndirect 6CJMP$4241

4142

PCHPCL

$4241 $4242Memory

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 6C 41 42JMP($4241); JumpIndirect 2C 57 42BIT$4257; TestBits w /Accum .Absolute 2CBIT$4257

5742
$4257Memory ($4257)^A!Z, ($4257)!N, V, -, -, -, -, -, - The byte at address $4257 is read and bits 7 and 6 are stored in flags N and V. The value is ANDed with the accumulator and the Z flag is set on a zero result The most bizarre of 6502 instructions:CMPwith logical AND instead of subtraction, but also stores the MSB and 6SB into N and V.

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 6C 41 42JMP($4241); JumpIndirect 2C 57 42BIT$4257; TestBits w /Accum .Absolute 2CBIT$4257

5742
$4257Memory Z N V

Other Instructions001modeopcode

A0 42LDY#$42; LoadY Immediate 94 42STY$42,X; StoreY Zero Page Indexed by X C4 42CPY$42; CompareY Zero Page EC 50 42CPX$4250; CompareX Absolute 4C 40 42JMP$4240; JumpAbsolute 6C 41 42JMP($4241); JumpIndirect 2C 57 42BIT$4257; TestBits w /Accum .Absolute 2CBIT$4257

5742

ANDA$4257Memory

Z N V

Single-Byte Data Instructions0xy01op1

E8INX;IncrementX CADEX;DecrementX C8INY;IncrementY 88DEY;DecrementY AATAX;TransferAccumulator to X A8TAY;TransferAccumulator to Y 8ATXA;TransferX to Accumulator 98TYA;TransferY to Accumulator BATSX;TransferStack Pointer to X 9ATXS;TransferX to Stack Pointer

Single-Byte Flag Instructions00011flag

18CLC;ClearCarry Flag 38SEC;SetCarry Flag 58CLI;ClearInterrupt Disable 78SEI;SetInterrupt Disable B8CLV;ClearOverflow Flag Set and clear the carry flag; useful withADCandSBC

Enable and disable interrupts. Useful for critical regions

Clear the overflow flag

Single-Byte Flag Instructions00011flag

18CLC;ClearCarry Flag 38SEC;SetCarry Flag 58CLI;ClearInterrupt Disable 78SEI;SetInterrupt Disable B8CLV;ClearOverflow Flag D8CLD;ClearDecimal Mode ( ADC,SBC perform binary arithmetic )F8SED;SetDecimal Mode ( ADC,SBC perform BCD arithemtic )In decimal mode,ADCandSBC

perform BCD arithmetic.In decimal mode, $19 + $1 = $20

In binary mode, $19 + $1 = $1A

US Patent 3,991,307 (1976) describes the 6502"s decimal adjust logic The 6502-based Ricoh 2A03 used in the Famicom/Nintendo Entertainment

System does not support decimal mode

Branch Instructions00001vflag

10 FE STARTBPLSTART; Branchon Plus N =030 0ABMIEND; Branchon Minus N =150 FABVCSTART; Branchon Overflow Clear V =070 06BVSEND; Branchon Overflow Set V =190 F6BCCSTART; Branchon Carry Clear C =0B0 02BCSEND; Branchon Carry Set C =1D0 F2BNESTART; Branchon Not Equal Z =0F0 FE ENDBEQEND; Branchon Equal Z =1Conditionally branch depending on the state of one of the four flags

Branch destination is program-counter-relative: between128 and 127 bytes

UseJMPto branch farther

BNEandBEQcould be called "branch on non-zero" and "branch on zero"

The 65C02 added the unconditionalBRAinstruction

Stack Instructions0op0op000

20 ED FDJSR$FDED; Jumpto Subroutine 60RTS;Returnfrom Subroutine For subroutine linkage:

JSR$FDED pushes the program counter onto the stack then jumps to $FDED RTSpops the program counter value off the stack, returning to just after the

JSRthat sent it there

Stack Instructions0op0op000

20 ED FDJSR$FDED; Jumpto Subroutine 60RTS;Returnfrom Subroutine 40RTI;Returnfrom Interrupt Return from an interrupt by popping the status register and the program

counter from the stack. (LikeRTS, but also restores the status register) Useful in interrupt routines and returning fromBRK

Stack Instructions0op0op000

20 ED FDJSR$FDED; Jumpto Subroutine 60RTS;Returnfrom Subroutine 40RTI;Returnfrom Interrupt 08PHP;PushProcessor Status 28PLP;PullProcessor Status 48PHA;PushAccumulator 68PLA;PullAccumulator Save and restore the processor status on the stack

Save and restore the accumulator on the stack

Typical processors encourage functions to save registers on the stack, but the

6502"s cramped (256 byte) stack demands parsimony

Stack Instructions0op0op000

20 ED FDJSR$FDED; Jumpto Subroutine 60RTS;Returnfrom Subroutine 40RTI;Returnfrom Interrupt 08PHP;PushProcessor Status 28PLP;PullProcessor Status 48PHA;PushAccumulator 68PLA;PullAccumulator 00BRK;BreakEANOP;Nooperation BRKis a software interrupt that pushes the current program counter and

status register on the stack before jumping to the break vector stored (in

ROM) at $FFFE.

NOPdoes nothing for two cycles. Useful in delay loops or to patch a program in memory.

Hello World in 6502 Assembly

ORG $8000

Set code origin

COUT EQU $FDED

Define

COUT label character out

ENTRYLDX#0; Use X because COUT leaves it unchanged LOOPLDAMSG,X; Get character from string BEQDONE; Are we at the end ?JSRCOUT; No :print the character INX;Go to next character in string BNELOOP; A trick :always taken DONERTS;Return MSG ASC "Hello World!"; Generate ASCII character code s

DB $8D,00

Define

byte 8 D is return 00 is end

Printed Assembler Output

1 ORG $8000

Set code origin 2

3 COUT EQU $FDED

Define

COUT label character outquotesdbs_dbs14.pdfusesText_20