Embedded system designers need low power devices in general. It is a prime consideration for device selection for battery powered devices. Many mixed signal systems, real time instrumentation in particular, fall into this category. Texas Instrument's MSP 430 family of microcontrollers is positioned precisely at this segment. Power consumption of these devices is very low and individual devices have a range of analog and digital peripherals on an on-chip communication bus within the chip. This high level of integration and a sophisticated interrupt structure makes these devices a good fit for designs. Processing power provided by the processors range from 8 to 25 MIPS. There are five subfamilies within this family of 163 devices. Clock management and a sophisticated power management are designed to minimize power consumption.

Choose a device from the large selection based on the configuration and the peripherals that are integrated into it. These include besides a 16 bit RISC CPU, Flash memory controller, DMA controller, hardware multiplier, Digital I/O, Watch dog timer, general purpose times, real time timers, USART that can be configured for UART, SPI or I2C communication, comparator, ADC and DAC, LCD controller, scan I/f and embedded emulation modes. The JTAG adapter provides the necessary access. The scan interface and the emulation modes are useful for development phase. The devices are memory mapped and connected to the system address and data buses through an adapter that adjust the data bus to 8 bit width. The buses are classical memory address bus and memory data bus and the devices are memory mapped.
The program memory model is that of one linear space. The top area is allocated to Flash/ROM and Interrupt vectors and bottom most areas are for special function registers and 8 bit and 16 bit devices. Memory space available varies according to the specific controller but the relative allocation remains same.

The programming model consists of this linear memory space, a set of registers and useful addressing modes. Besides an ALU the CPU has a set of 16 general purpose registers R0-R15. R0 is dedicated as the program counter, R1 as stack pointer, R2 as the status register and constant generator CH1 and R3 as constant generator CG2. Rest of the registers is fully general purpose registers.

Being RISC mode CPUs complex addressing modes is not used. The ones used are the register mode, indexed mode, symbolic mode, absolute mode, indirect register mode, indirect auto-increment and immediate mode. Except for the Symbolic mode all the modes have classical meaning. Symbolic mode is the PC relative mode in those terms. Programming tool chains, evaluation boards, integration tools and JTAG based debug support are available from a range of manufacturers. That includes quite a few free source tools. So if you are into low power embedded design and mixed signal/instrumentation and battery powered projects, in particular, you have everything that you need available.

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