Commonly in space systems there are subsystems or instruments with a low or null communication or processing capabilities. This paper describes a high reliable, low power consumption and small sized Remote Terminal Unit aimed at connecting these subsystems to the satellite's system bus. The design includes a SoC based on an 80C32 microcontroller and provides a 2.0 CAN controller; a general purpose digital I/0s; ADCs interfaces; and one UART interface. As key features concerning fault tolerance, the proposed system uses space qualified components; hardware redundancy is considered; it has auto-check capabilities; and if necessary, the embedded generic firmware allows remote downloading of updated versions of flight software through the CAN bus and, in the same way, by means of a CAN message the full system can be restarted by the spacecraft control system.