16 MHz MSP430 core with 4 KB flash
The MSP430F2121IPWR is a 16-bit microcontroller from the MSP430F2xx family, built around the MSP430 CPU16 core clocked at 16 MHz.
On-chip brown-out reset and power-on reset protect against glitchy power-up sequences — a common headache in battery-powered designs where the supply ramps slowly.
Package and board-fit
Housed in a 20-pin TSSOP (4.40 mm wide), this is a hand-solderable SMD package — fine for prototype rework or low-volume assembly. The 0.65 mm pitch is forgiving under a magnifier, and the small footprint leaves room on a two-layer board. Tape-and-reel packaging (Cut Tape also available) means it feeds into pick-and-place for production runs, but you can also grab a few loose samples for breadboarding.