SECURITY CIRCUIT

PURPOSE:To hold security by inhibiting read-out by a read-out inhibiting circuit, in the case a security code and a key code do not coincide with each other, and executing read-out in the case they coincide with each other. CONSTITUTION:In the case a security code and a key code compared by a comparing circuit 4 do not coincide with each other, a comparison output signal becomes '0', and an output of a NOT circuit 10 becomes '1'. Also, since an enable signal of a flip-flop 7 is '1', an output signal of a NOD circuit 11 becomes '0' and is written in a memory 12, and held. When it is written in the memory 12, its output signal. becomes '0'. Accordingly, an RE signal of an output of an AND circuit 8 being a read-out inhibiting means always becomes '0', and read-out of data stored in a memory 13 contained in a microcomputer, etc., becomes impossible unless data in the memory 12 is erased.