Cortex-M3 at 25 MHz with 16 KB Flash
The Texas Instruments LM3S300-EGZ25-C2T is a Stellaris® family 32-bit MCU built around the ARM® Cortex®-M3 core running at 25 MHz. It packs 16 KB of on-chip Flash and 4K x 8 bytes of SRAM, enough for a modest control loop or sensor fusion task without external memory.
Package, temperature grade, and board-fit
The internal oscillator means you can skip an external crystal for many applications, saving two pins and a couple of passives — though if you need tight timing for a UART baud rate, you'll still want a resonator.
On-chip peripherals and serial connectivity
Beyond the serial interfaces, the MCU includes a brown-out detect/reset, a power-on reset, a PWM module, and a watchdog timer — enough to build a simple motor controller or a safety watchdog without an external supervisor IC. The 16 KB Flash and 4 KB SRAM budget is tight for a full RTOS but comfortable for a bare-metal state machine or a lightweight scheduler like protothreads.