  Designing integrated circuits in radiation environments such as the High
Luminosity LHC (HL-LHC) is challenging. Integrated circuits will be exposed to
radiation-induced Single Event Effects (SEE). In deep sub-micron technology
devices, the impact of SEEs can be mitigated by triple modular redundancy. The
triplication of the most sensitive data is used to recover most of the data
corruption induced by interacting particles. One type of SEE, called single
event upset (SEU), is studied in this paper. The SEU cross-section and the
performance of the triplication are estimated using an ASIC prototype exposed
to a beam of protons. The SEU cross-section is measured, and a systematic
difference between $1\rightarrow{0}$ and $0\rightarrow{1}$ bit flip rates is
observed. The efficiency of the mitigation method is investigated.
