Patent ID: 7325144

Claim:
A portable information processing device ( 10 ) having a checking function for an input password code, said portable information processing device comprising: a rewritable non-volatile memory ( 11 ) which holds stored contents even after supply of power has been cut off; and a control device ( 12 ) for accessing said rewritable non-volatile memory, wherein said rewritable non-volatile memory ( 11 ) is a memory in which unit areas (U 1 to U 6 ) are defined, an erasure process and a subsequent changing process are required to write data bits into at least a specific one of said unit areas, all said data bits in said specific one of said unit areas being set to a first logic state in said erasure process and desired ones of said data bits in said specific one of said unit areas being changed from said first logic state to a second logic state in said subsequent changing process, and a predetermined password code and a checking requirement flag bit or bits, which indicates whether or not checking by said predetermined password code is required, are stored, wherein said control device ( 12 ) has a function whereby, in a case where said checking requirement flag indicates said checking is required, predetermined processes are executed when said input password code and said predetermined password match in a checking process, and in a case where said checking requirement flag indicates said checking is not required, said predetermined processes are executed without performing said checking process, and wherein said control device ( 12 ) further has a function of attaching a predetermined error check code to data to be stored in a writing process into said rewritable non-volatile memory ( 11 ), and a function of judging whether or not said predetermined error check code attached to data is correct in a process reading from said non-volatile memory ( 11 ) and handling data that have been so read as correct data under the condition that said predetermined error check code attached to data is correct, characterized in that said control device ( 12 ) is equipped with processing functions whereby said checking requirement flag bit or bits is handled as indicating the “required” state when said checking requirement flag bit or bits are in said first logic state, said checking requirement flag bit or bits is handled as indicating the “not required” state when said checking requirement flag bit or bits are in said second logic state, an error check code is prevented from being attached in a process of writing said checking requirement flag bit or bits, and said checking requirement flag bit or bits is always handled without an error check code in reading said checking requirement flag bit or bits.