The package of the Mercury Plasma Particle Experiment (MPPE) on board the Mercury Magnetosphere Orbiter (MMO) of the Bepi-Colombo Mission includes an advanced Mass Spectrum Analyzer (MSA) dedicated to measurements of mass-resolved low energy 3-D ion distributions. The MSA instrument consists of a top-hat electrostatic analyzer combined with a Time-Of-Flight (TOF) spectrometer providing an unprecedented mass resolution (m/Δm=40 for ion energies < 15 keV and m/Δm=15 for ion energies > 15 keV) in the energy range 5 eV/q – 40 keV/q at 64 energy steps. The instrument Field of View is 8 deg X 360 deg with an angular resolution of 8 ded X 11.25 deg. The time resolution for measurements of the 3-D distribution function is 2 sec (half spin period). The MSA/CPU to be developed by DUTH/SRL is based on discrete Rad Hard devices and is implemented using specific fault tolerant design techniques. The CPU is designed to handle a raw data rate of 4 Mbps (out of a total of 4.9 Mbps of the MPPE package), to acquire Housekeeping data, to interface to the TOF unit and the TC/TM board, to control the High Voltage Power Supplies of the electrostatic analyzer and to derive science data from the onboard processing of engineering raw data.