Open Source Soft Core, protected against SEU for the ALICE Inner Tracking System at the CERN Large Hadron Collider. The thesis subject is developed in the framework of the Inner Tracking System (ITS) Detector construction in view of its installation in the ALICE experiment running at the CERN Large Hadron Collider. A brief analysis of the different open source ISAs and protection of a microcontroller that implements Fault Tolerant design and specific peripherals will be performed. The core will be programmed on the Xilinx Kintex Ultrascale mounted on the Readout Unit V1 used for the ALICE ITS; for this reason the main goal of the thesis is to reach good performances in terms of protection against SEUs.