A memory protection system includes an auxiliary power supply source for maintaining information stored in a random access memory when the main power supply is terminated. When the main power supply voltage level becomes lower than a preselected level, a detection unit develops a control signal for applying a disabling signal to a chip selection terminal included in the random access memory, whereby a load such as a central processor unit connected to the random access memory is electrically disconnected from the random access memory to minimize the power dissipation.