Instruction Set

RRA[.W]

Rotate right arithmetically

 

RRA.B

Rotate right arithmetically

 

Syntax

RRA

dst

or

RRA.W dst

 

RRA.B

dst

 

 

Operation

MSB −> MSB, MSB −> MSB−1, ... LSB+1 −> LSB, LSB −> C

Description

The destination operand is shifted right one position as shown in Figure 3−16.

 

The MSB is shifted into the MSB, the MSB is shifted into the MSB−1, and the

 

LSB+1 is shifted into the LSB.

 

Figure 3−16. Destination Operand—Arithmetic Right Shift

Word

15

0

C

 

 

Byte

 

 

 

15

0

Status Bits

N: Set if result is negative, reset if positive

 

Z:

Set if result is zero, reset otherwise

 

C:

Loaded from the LSB

 

 

V:

Reset

 

 

Mode Bits

OSCOFF, CPUOFF, and GIE are not affected.

Example

R5 is shifted right one position. The MSB retains the old value. It operates

 

equal to an arithmetic division by 2.

 

RRA

R5

; R5/2 −> R5

;

The value in R5 is multiplied by 0.75 (0.5 + 0.25).

;

 

 

 

 

 

PUSH

R5

; Hold R5 temporarily using stack

 

RRA

R5

; R5 0.5 −> R5

 

ADD

@SP+,R5

; R5 0.5 + R5 = 1.5 R5 −> R5

 

RRA

R5

; (1.5 R5) 0.5 = 0.75 R5 −> R5

 

......

 

 

 

Example

The low byte of R5 is shifted right one position. The MSB retains the old value.

 

It operates equal to an arithmetic division by 2.

 

RRA.B

R5

; R5/2 −> R5: operation is on low byte only

 

 

 

 

; High byte of R5 is reset

 

PUSH.B

R5

; R5 0.5 −> TOS

 

RRA.B

@SP

; TOS 0.5 = 0.5 R5 0.5 = 0.25 R5 −> TOS

 

ADD.B

@SP+,R5

; R5 0.5 + R5 0.25 = 0.75 R5 −> R5

......

3-60

RISC 16−Bit CPU

Page 96
Image 96
Texas Instruments MSP430x1xx manual Rra.W, Rra.B

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.