The STC12C5404AD-35I-DIP20 (or STC MCU) is a 35 MHz Microcontroller Units (CPUs/MPUs/SOCs) manufactured by STC. It is an 8-bit device powered by an edge-triggered single-cycle, 4K X 512 Byte Flash 15 5 Series with 15 single-cycle instruction cycles per machine cycle. It has up to 28K Bytes of Program Flash and its function is fully static. It has 8 X 8-bit I/O ports and 26 Interrupt sources, including external interrupt INT0/INT1/INT2/INT3 and I2C Interrupt. It also supports serial port UART, I2C interfaces, SPI interface, clock output, power-down/idle modes, and a variety of power saving options. Plus, it is RoHS compliant. This device is most suitable for low power applications while still maintaining a high level of performance.