Addressing Modes

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

@Rn

Rn is used as a pointer to the

 

mode

 

operand.

11/−

Indirect

@Rn+

Rn is used as a pointer to the

 

autoincrement

 

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.

RISC 16-Bit CPU

3-9

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Texas Instruments MSP430x1xx 3. Source/Destination Operand Addressing Modes, As/Ad Addressing Mode Syntax Description
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MSP430x1xx specifications

The Texas Instruments MSP430x1xx series is a family of ultra-low-power microcontrollers that are highly regarded in the embedded systems community for their versatility and performance. Designed for applications ranging from portable instrumentation to low-power industrial devices, the MSP430x1xx combines flexibility and efficiency with advanced features tailored for energy-sensitive applications.

One of the standout characteristics of the MSP430x1xx is its ultra-low-power operation. This series offers several low-power modes that can significantly extend battery life in portable devices. The microcontroller can be in active mode, low-power mode, or even in a deep sleep state, allowing developers to optimize power consumption based on the application's requirements. In fact, some configurations can operate at just a few microamps, making it ideal for battery-operated devices.

Another key feature is the 16-bit RISC architecture that provides powerful processing capabilities while maintaining a low power profile. The MSP430x1xx series supports a maximum clock speed of 16 MHz, allowing for efficient task execution while consuming minimal energy. This architecture ensures that programs run smoothly while the microcontroller remains energy efficient.

The MSP430x1xx is equipped with various integrated peripherals, including analog-to-digital converters (ADCs), timers, and communication interfaces like UART, SPI, and I2C. The inclusion of a powerful ADC enables the microcontroller to handle sensor readings with high accuracy, making it suitable for applications like environmental monitoring and medical devices. The integrated timers provide essential functionality for real-time applications, allowing for event-driven programming and precise timing control.

Memory options in the MSP430x1xx series are also robust, with configurations offering flash memory sizes from 1 KB to 64 KB. This flexibility allows developers to choose the optimal memory size for their specific applications, accommodating a wide range of requirements.

Additionally, the MSP430x1xx microcontrollers are designed with a wide operating voltage range, typically from 1.8V to 3.6V, making them compatible with various power sources and further enhancing their usability in diverse applications.

In summary, the Texas Instruments MSP430x1xx series of microcontrollers is an excellent choice for developers seeking low-power, high-performance solutions for embedded applications. With an efficient architecture, a rich set of peripherals, and flexible memory options, these microcontrollers are positioned to meet the growing demands of modern electronic designs, particularly in battery-powered and energy-sensitive applications.
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