Error detection control system

1. An error detection control system comprising:

a nonvolatile memory having data areas for a plurality of addresses, the data areas each including a main data area for storing predetermined data and a redundant data area for storing redundant data to be used in an error detecting process on the data;

memory control means for controlling on the nonvolatile memory a batch erasing process on a data area group basis, the data area group including the data areas of a predetermined number of addresses, a reading process on the data area basis, a programming process on the data area basis, and an overwriting process on the main data area after the programming process on a bit basis, the bit constituting the main data area;

error detecting means for executing the error detecting process on read-out data in the reading process, based upon the corresponding redundant data; and

error detecting control means for controlling availability of execution of the error detecting process on the read-out data by the error detecting means, based upon data types to be classified depending on whether or not the read-out data is subjected to the overwriting process or a storage state indicating whether or not the overwriting process has been executed.

2. The error detection control system according to claim 1 , wherein

the nonvolatile memory is configured such that each of the data areas is set to an error detection process inhibit data area for storing the data on which the execution of the error detecting process is inhibited or an error detection process permit data area for storing the data on which the execution of the error detecting process is permitted, and

the error detecting control means inhibits the error detection means from executing the error detecting process during the reading process when a reading object data area to be subjected to the reading process corresponds to the error detecting process inhibit data area, and permits the error detection means to execute the error detecting process during the reading process when the reading object data area corresponds to the error detecting process permit data area.

3. The error detection control system according to claim 1 , wherein

the memory control means outputs an error detection control signal to the error detection control means in the reading process in accordance with the data type of the read-out data in the reading process,

the error detection control means determines whether or not the data type of the read-out data corresponds to a data type allowing the overwriting process to be executed based upon the error detection control signal in the reading process, permits the error detection means to execute the error detecting process when the data type corresponds to a data type not allowing the overwriting process to be executed, and inhibits the error detection means from executing the error detecting process when the data type corresponds to a data type allowing the overwriting process to be executed, and

the error detection means executes the error detecting process on the read-out data by using the corresponding redundant data when the execution of the error detecting process on the read-out data is permitted by the error detection control means.

4. The error detection control system according to claim 3 , wherein

when the error detection control signal is a signal indicating that the read-out data corresponds to command data, the error detection control means permits the execution of the error detecting process, and

when the error detection control signal is a signal indicating that the read-out data corresponds to a program counter value, the error detection control means inhibits the execution of the error detecting process.

5. The error detection control system according to claim 1 , wherein

the nonvolatile memory comprises a flag area for storing the availability of the execution of the error detecting process for each of the data areas, and

the error detection control means sets an execution inhibit flag for the error detecting process in the flag area corresponding to the data area to be subjected to be the overwriting process when the memory control means carries out the overwriting process.

6. The error detection control system according to claim 1 further comprising

a register configured to store the availability of the execution of the error detecting process for each of the data areas outside the nonvolatile memory, wherein

the error detection control means sets in the register an execution inhibit flag for the error detecting process on the data area to be subjected to be the overwriting process when the memory control means carries out the overwriting process.

7. The error detection control system according to claim 1 , wherein

the memory control means carries out the reading process on an error detection inhibit data on which the execution of the error detecting process is inhibited, and then further carries out the reading process on the error detection inhibit data a predetermined number of times, and

the error detection control means compares respective read-out data in the reading process and determines whether the read-out data is correct or incorrect.

8. The error detection control system according to claim 1 , wherein

the redundant data is designed to be applicable to an error correcting process in addition to the error detecting process,

the error detection means executes the error detecting process and the error correcting process on the read-out data based upon the corresponding redundant data, and

the error detection control means inhibits execution of the error correcting process when it inhibits the execution of the error detecting process.

9. An IC card comprising

an IC chip in which the error detection control system according to claim 1 is installed.