The ST21F384 secure MCU for smart cards is based on an enhanced 8/16-bit CPU core running, typically, at 21 MHz, and built using a 90-nm process. It has a 16-Mbyte linear addressing space and employs a serial interface fully compatible with the ISO 7816-3 standard.

The MCU embeds 7 Kbytes of user RAM, plus 384 Kbytes of flash, organized as 128-byte pages, and includes a hardware Data Encryption Standard accelerator and a user-accessible CRC calculation block. The chip has 3-ms page erase time and comes as sawn or unsawn wafers, and in six-contact (D17) and eight-contact (D95) RoHS-compliant modules.