Master Mode | Texas Instruments MSP430x1xx instruction

USART Operation: SPI Mode

14.2.2 Master Mode

Figure 14−2. USART Master and External Slave

		MASTER	SIMO	SIMO	SLAVE
			SIMO	SIMO
Receive Buffer UxRXBUF		Transmit Buffer UxTXBUF			SPI Receive Buffer
			Px.x	STE
			STE	SS
			STE	Port.x
				Port.x
Receive Shift Register			SOMI	SOMI
Receive Shift Register		Transmit Shift Register		Data Shift Register (DSR)
MSB	LSB	MSB	LSB	MSB	LSB
	MSP430 USART		UCLK	SCLK	COMMON SPI
	MSP430 USART				COMMON SPI

Figure 14−2 shows the USART as a master in both 3-pin and 4-pin configurations. The USART initiates data transfer when data is moved to the transmit data buffer UxTXBUF. The UxTXBUF data is moved to the TX shift register when the TX shift register is empty, initiating data transfer on SIMO starting with the most-significant bit. Data on SOMI is shifted into the receive shift register on the opposite clock edge, starting with the most-significant bit. When the character is received, the receive data is moved from the RX shift register to the received data buffer UxRXBUF and the receive interrupt flag, URXIFGx, is set, indicating the RX/TX operation is complete.

A set transmit interrupt flag, UTXIFGx, indicates that data has moved from UxTXBUF to the TX shift register and UxTXBUF is ready for new data. It does not indicate RX/TX completion.

To receive data into the USART in master mode, data must be written to UxTXBUF because receive and transmit operations operate concurrently.

Four-Pin SPI Master Mode

In 4-pin master mode, STE is used to prevent conflicts with another master. The master operates normally when STE is high. When STE is low:

-SIMO and UCLK are set to inputs and no longer drive the bus

-The error bit FE is set indicating a communication integrity violation to be handled by the user

A low STE signal does not reset the USART module. The STE input signal is not used in 3-pin master mode.

USART Peripheral Interface, SPI Mode

14-5

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.

Texas Instruments MSP430x1xx manual Four-Pin SPI Master Mode

Models: MSP430x1xx