The EM78611 is a series of Universal Serial Bus 8-bit RISC microcontrollers. It is specifically designed for USB low speed device application and to support legacy device such as PS/2 keyboard. The EM78611 also support one device address and three endpoints. With no firmware involved, these series of microcontrollers can automatically identify and decode Standard USB Command to EndPoint Zero. The EM78611 is implemented on a RISC architecture. It has eight-level stack and six interrupt sources. Each device has 144 bytes of general purpose SRAM and 6K bytes of program ROM. The EM78611 has up to 13 pins with the capacity of sinking large current. It also has dual clock mode which allows the device to run on very low power saving frequency