In this paper, we present a SpaceWire router IP protected against soft errors by using design level fault tolerance techniques. In order to obtain a low overhead and high protection, a fault injection experiment was performance to evaluate the most susceptible functions in the protocol. Based in the results, fault detection techniques were implemented in RTL level just in the most critical elements. Final results show that the error detection capability of the proposed IP increases in more than 100% with minimal area and performance overhead. The IP targets ASIC or Flash-FPGA platforms. © 2011 IEEE.