The access time for the use of an electronic device, for example a chip, is prolonged
after each unauthorized access attempt. The access time is determined by the time
for the matching of the turn-on voltages of two floating gate cells. Before an
access attempt, the turn-on voltage of one cell is set to a predefined initial
value and the turn-on voltage of the other cell is set to a value which is higher
in comparison and which is increased after each unauthorized access.