The MCU (Micro-Controller Unit) used on the kit is a low-power 16-bit of the Texas Intruments MSP430 micro-controller family.
The MCU features:
low voltage supply (1.8V - 3.6V)
low current consumption (330uA in active mode at 1MHz and 2.2V, 1.1uA in stand-by mode, 0.2uA in off mode)
16-bit RISC architecture, 125ns instruction cycle
48KB FLASH memory, 2kB RAM memory (92kB FLASH and 8kB RAM in case of FITkit 2.0)
Additional features:
3-channel DMA
16-bit timers Timer_A, Timer_B
comparator unit
serial communication interfaces USART0 (asynchronous UART, synchronous SPI, I2C), USART1 (asynchronous UART, synchronous SPI)
12-bit A/D and D/A converter
The 1.x FITkit version contains the MSP430F168IPM MCU, whereas the 2.0 FITkit version has a more powerful MCU the MSP430F2617.