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Commodore Plus 4
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£96
Machine
Language
on
the
Commodore
Plus/4
The
following
instructions
are
available
in
absolute
indexed
mode
using
the
X
register:
ADC,
AND,
ASL,
CMP,
DEC,
EOR,
INC,
LDA,
LDY,
LSR,
ORA,
ROL,
ROR,
SBC,
and
STA.
In
the
machine-language
monitor,
an
absolute
indexed
mode
instruction
using
the
Y
register
appears
in
this
form:
mnemonic
$hlilih,Y
where
mnemonic
is
an
instruction
mnemonic
and
h
represents
a
hexadecimal
digit.
The
following
instructions are
available
in
absolute
indexed
mode
using
the
Y
register:
ADC,
AND,
CMP,
EOR,
LDA,
LDX,
ORA,
SBC,
and
STA.
Zero
Page
Indexed
Mode
In
this
mode,
either
the
X
register
or
the
Y
register
is
used
as
an
index.
The
address
of
the
operand
is
calculated
by
adding
the
value
of
the
index
to
the
specified
base
address.
An
instruction
in
zero
page
indexed
mode
consists
of 2
bytes.
The
first
is
the
opcode
for
the
desired
instruction.
The
second
is
the
low
byte
of
the
base
address.
The
high
byte
of
the
base
address
is
assumed
to
be
zero
and
is
not
specified.
In
the
machine-language
monitor,
a
zero
page
indexed
mode
instruction
using
the
X
register
appears
in
this
form:
mnemonic
$lili,X
where
mnemonic
is
an
instruction
mnemonic
and
h
represents
a
hexadecimal
digit.
The
following
instructions
are
available
in
zero
page
indexed
mode
using
the
X
register:
ADC,
AND,
ASL,
CMP,
DEC,
EOR,
INC,
LDA,
LDY,
LSR,
ORA,
ROL,
ROR,
SBC,
STA,
and
STY.
In
the
machine-language
monitor,
a
zero
page
indexed
mode
instruction
using
the
Y
register
appears
in
this
form:
mnemonic
$lili,Y
where
mnemonic
is
an
instruction
mnemonic
and
h
represents
a
hexadecimal
digit.
The
following
instructions
are
available
in
zero
page
indexed
mode
using
the
Y
register:
LDX
and
STX.
Note:
In
zero
page
indexed
mode,
the
address
of
the
operand
is
always
on
zero
page.
For
example,
if
the
X
register
contains
$04
and
the
instruction
LDA
$FE,X
is
executed,
the
value
found
in
location
$02
will
be
loaded
into
the
accumulator.
Indirect
Indexed
Mode
In
this
mode
the
Y
register
is
used
as
the
index.
The
base
address
is
found
indirectly
in
the
zero
page
location
specified
with
the
instruction.

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