The STMicroelectronics Ultra low power microcontrollers based on the high performance Arm Cortex -M0+ 32 bit RISC core operating at a frequency of up to 56 MHz The device embed high speed memories up to 256 Kbyte flash memory and 40 Kbyte SRAM with hardware parity check, and an extensive range of enhanced I/Os and peripherals connected to APB and AHB buses, and a 32 bit multi AHB bus matrix. They also embed protection mechanisms for embedded flash memory and SRAM, such as readout protection and write protection.

4 to 48 MHz crystal oscillator
32 kHz crystal oscillator for RTC
Internal 16 MHz factory trimmed
Customer code protection
Hardware protection feature
Secure boot
5 passive anti tamper pins