The STM8S003F3U6TR is an 8-bit microcontroller from ST's STM8S value line, built around the STM8 core running at 16 MHz.
The 16 MHz clock is the maximum CPU frequency. For a typical instruction-execution mix (most single-cycle, some multi-cycle), the effective throughput lands around 8 to 12 MIPS. That is enough for a 100 kHz control loop, a UART at 115200 baud, or a SPI transaction at a few megabits per second. If your application needs to run a PID loop at 10 kHz while polling an ADC and updating a display, this part has the headroom.
Memory sizing — 8 KB Flash, 1 KB RAM, 128 B EEPROM
The 8 KB Flash is the firmware budget. A typical UART bootloader plus a simple state machine fits in under 4 KB, leaving room for a modest application. The 1 KB RAM handles a few dozen variables and a small buffer — enough for a 256-byte UART FIFO and a 64-byte sensor data structure. If your firmware needs more than 8 KB of code space, you will need to step up to the STM8S103 or STM8S105 family.
It is suited for reflow assembly and fits on tight PCBs where every square millimetre counts.
ST lists the STM8S003F3U6TR as Active.