The STM32F21x family is based on the high-performance ARM® Cortex™-M3 32-bit RISC core operating at a frequency of up to 120 MHz. The family incorporates high-speed embedded memories (Flash memory up to 1 Mbyte, up to 128 Kbytes of system SRAM), up to 4 Kbytes of backup SRAM, and an extensive range of enhanced I/Os and peripherals connected to two APB buses, three AHB buses and a 32-bit multi-AHB bus matrix.

The devices also feature an adaptive real-time memory accelerator (ART Accelerator™) which allows to achieve a performance equivalent to 0 wait state program execution from Flash memory at a CPU frequency up to 120 MHz. This performance has been validated using the CoreMark benchmark.