3 addressing modes – Texas Instruments MSP430x4xx User Manual

Page 43

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Addressing Modes

3-9

RISC 16-Bit CPU

3.3

Addressing Modes

Seven addressing modes for the source operand and four addressing modes
for the destination operand can address the complete address space with no
exceptions. The bit numbers in Table 3−3 describe the contents of the As
(source) and Ad (destination) mode bits.

Table 3−3. Source/Destination Operand Addressing Modes

As/Ad

Addressing Mode

Syntax

Description

00/0

Register mode

Rn

Register contents are operand

01/1

Indexed mode

X(Rn)

(Rn + X) points to the operand. X
is stored in the next word.

01/1

Symbolic mode

ADDR

(PC + X) points to the operand. X
is stored in the next word. Indexed
mode X(PC) is used.

01/1

Absolute mode

&ADDR

The word following the instruction
contains the absolute address. X
is stored in the next word. Indexed
mode X(SR) is used.

10/−

Indirect register
mode

@Rn

Rn is used as a pointer to the
operand.

11/−

Indirect
autoincrement

@Rn+

Rn is used as a pointer to the
operand. Rn is incremented
afterwards by 1 for .B instructions
and by 2 for .W instructions.

11/−

Immediate mode

#N

The word following the instruction
contains the immediate constant
N. Indirect autoincrement mode
@PC+ is used.

The seven addressing modes are explained in detail in the following sections.
Most of the examples show the same addressing mode for the source and
destination, but any valid combination of source and destination addressing
modes is possible in an instruction.

Note:

Use of Labels EDE, TONI, TOM, and LEO

Throughout MSP430 documentation EDE, TONI, TOM, and LEO are used
as generic labels. They are only labels. They have no special meaning.

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