It carries 15.5 KB of FRAM program memory and 2 KB of SRAM, with 52 general-purpose I/O lines. FRAM is the key differentiator here: it unifies code and data storage in a single non-volatile memory that writes at bus speed, draws near-zero standby power, and endures 10^15 write cycles — no separate EEPROM needed, no Flash page-erase penalty.
FRAM memory — the design decision that changes the firmware strategy
15.5 KB of FRAM is both the program store and the data EEPROM. There is no separate Flash-to-RAM copy step on boot — code executes directly from FRAM, and variables can live in the same space without wear-leveling logic. For a firmware engineer, this means field updates over I²C or UART are simpler: you write new code directly to FRAM at byte granularity, no erase cycle, no sector management. The 2 KB SRAM is available for stack and scratch buffers. The internal oscillator is the default clock source, so the board needs no external crystal for most applications, though the clock tree supports external sources if timing accuracy demands it.
56-TSSOP package — footprint for the PCB layout engineer
The MSP430FR4133IG56 comes in a 56-lead TSSOP (body 6.10 mm wide, 0.5 mm pitch, per the 56-TFSOP case code). Surface-mount only. The 52 I/O are on a fine-pitch leadframe — no exposed pad, so thermal dissipation is through the leads only. Decoupling: a 0.1 µF ceramic per supply pin pair, placed as close to the package as the pitch allows, with a bulk 4.7 µF or 10 µF on the board-level 3.3 V rail. The 1.8 V minimum supply means a single Li-ion cell or two alkaline cells can power the MCU directly if the application can tolerate the voltage droop.
For the procurement desk: this part does not carry a single-source risk flag — TI's MSP430 FRAM family has multiple density and package variants, but the IG56 (56-TSSOP) is the specific footprint. If a second-source or drop-in alternate is needed, the closest pin-compatible sibling within the same family would be another MSP430FR4xxx in the 56-TSSOP package — verify the FRAM size and peripheral set against the BOM requirements.