The MSP430 is a mixed-signal microcontroller family from Texas Instruments, first introduced on 14 February 1992. Built around a CPU, the MSP430 was designed for use with low power consumption embedded applications and for low cost.
Applications
The MSP430 can be used for low powered embedded devices. The current drawn in idle mode can be less than 1 µA. It has a top CPU speed of 25 MHz. It can be throttled back for lower power consumption. The MSP430 also uses six different low-power modes, which can disable unneeded clocks and CPU, as well as wake-up in under 1 microsecond, allowing the controller to stay in sleep mode longer.
The device comes in a variety of configurations featuring the usual peripherals:
internal oscillator, timer including pulse-width modulation (PWM), watchdog timer (watchdog), USART, Serial Peripheral Interface (SPI) bus, Inter-Integrated Circuit (I²C), analog-to-digital converter (ADC) options: 10/12/14-bit successive-approximation ADC 16/24-bit delta sigma ADC internal analog comparator with digital timers can measure resistor-capacitor slope charging time and brownout reset circuitry.
Some less usual peripheral options include on-chip operational amplifiers (op-amp) for signal conditioning, 12-bit digital-to-analog converter (DAC), liquid crystal display (LCD) driver, hardware multiplier, USB, and direct memory access (DMA) for ADC results. Apart from some older erasable programmable read-only memory (EPROM, such as MSP430E3xx) and high volume mask ROM (MSP430Cxxx) versions, all of the devices are in-system programming enabled via Joint Test Action Group (JTAG), full four-wire or Spy-Bi-Wire), a built in bootstrapping loader (BSL) using UART such as RS-232, or USB on devices with USB support. No BSL is included in F20xx, G2xx0, G2xx1, G2xx2, or I20xx family devices.
Memory limitations
There are, however, limits that preclude its use in more complex embedded systems. The MSP430 does not have an external memory bus, so it is limited to on-chip memory, up to 512 KB flash memory and 66 KB random-access memory (RAM), which may be too small for applications needing large buffers or data tables. Also, although it has a DMA controller, it is very difficult to use it to move data off the chip due to a lack of a DMA output strobe.
MSP430 generations
Six general generations of MSP430 processors exist. In order of development, they are: '3xx generation, '1xx generation, '4xx generation, '2xx generation, '5xx generation, and '6xx generation. The digit after the generation identifies the model (generally higher model numbers are larger and more capable), the third digit identifies the amount of memory included, and the fourth, if present, identifies a minor model variant. The most common variation is a different on-chip analog-to-digital converter.
The 3xx and 1xx generations are limited to a 16-bit address space. In the later generations this was expanded to include '430X' instructions that allow a 20-bit address space. As happened with other processor architectures (e.g. the processor of the PDP-11), extending the addressing range beyond the 16-bit word size introduced some peculiarities and inefficiencies for programs larger than 64 kBytes.
In the following list, it helps to think of the typical 200 mA·Hr capacity of a CR2032 lithium coin cell as 200,000 μA·Hr, or 22.8 μA·year. Thus, considering only the CPU draw, such a battery could supply a 0.7 μA current draw for 32 years. (In reality, battery self-discharge would reduce this number.)
The significance of the RAM retention vs the real-time clock mode is that in real time clock mode the CPU can go to sleep with a clock running which will wake it up at a specific future time. In RAM retention mode, some external signal is required to wake it, e.g., input/output (I/O) pin signal or SPI slave receive interrupt.
MSP430x1xx series
The MSP430x1xx Series is the basic generation without an embedded LCD controller. They are generally smaller than the '3xx generation. These flash- or ROM-based ultra-low-power MCUs offer 8 MIPS, 1.8–3.6 V operation, up to 60 KB flash, and a wide range of analog and digital peripherals.
Power specification overview, as low as: 0.1 μA RAM retention 0.7 μA real-time clock mode 200 μA / MIPS active Features fast wake-up from standby mode in less than 6 µs.