The STM32F091Cx from STMicroelectronics is a Space Qualified Microcontroller with Clock Rate 32 kHz to 48 MHz, Operating Frequency 48 MHz, Internal RAM Memory SRAM : 32 kB, Flash Memory 128 to 256 kB, Supply Voltage 2 to 3.6 V. Tags: Surface Mount. More details for STM32F091Cx can be seen below.