Commodore Plus 4 - Page 270

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288

2008

S009

200B

200D

INX

CPX

BCC

BRK

#$20

$2002

Increment

Compare

$20.

less

than

$20,

back.

Stop

processing.

Use

the

(Memory)

command

examine

and

change

the

values

$2100-$211F.

CFY—Compare

Memory

with.

The

value

currently

the

compared

with

the

specified

operand

and

the

appropriate

flags

are

set.

Operation:

Y-M

Flags

Affected:

Addressing

Mode

Syntax

Opcode

Bytes

Cycles

Immediate

Zero

page

Absolute

CPY

#$hh

CPY

$hh

CPY

$hhhh

The

value

memory

subtracted

from

the

value

the

but

neither

value

altered.

The

following

table

shows

the

effect

each

the

flags.

The

flag

should

used

when

two's

complement

compare

required

(e.g.,

$FF

minus

and

less

than

$01).

The

flag

should be

used

when

unsigned

compare

required

(e.g.,

$FF

255

and

greater

than

$01).

Condition

Flag

memory

0 0

memory

Oil

memory

Example:

This

program

copies

the

contents

$2100-$21

$2110-$211F.

The

used

indirect

index

and

index.

The

CPY

instruction

used

determine

when

stop

copying.

2000

LDA

#$00

Load

with

zero.

2002

TAY

Load

with

zero.

2003

STA

$D8

Store

zero

the

low

indirect

address.

2005

LDA

#$21

Load

with

$21.

2007

STA

$D9

Store

$21

the

high

indirect

address.

Commodore Plus 4 - Page 270

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