Core parametrics and memory fit
The MSP430F2121TDGVR: 16-bit MSP430 CPU16 core clocked at 16 MHz — the 4 KB on-chip Flash plus 256 x 8 RAM suits lightweight control loops, sensor polling, and simple protocol handling where external memory adds cost. 16 general-purpose I/O with built-in Brown-out Detect, POR, PWM, and WDT reduces external supervisor and timer ICs, saving board area in a 20-TVSOP footprint.
