Abstract: Even if a plurality of tasks that access a plurality of data areas each having the different control method are operated in parallel and the access requests are generated almost simultaneously, the simultaneous accesses to the memory device can be prevented and also a plurality of tasks can be operated in parallel while maintaining a real-time characteristic since the access request contained in the tasks are divided into partial request units by the access-request mediating portion to switch the access requests.

Abstract: Even if a plurality of tasks that access a plurality of data areas each having the different control method are operated in parallel and the access requests are generated almost simultaneously, the simultaneous accesses to the memory device can be prevented and also a plurality of tasks can be operated in parallel while maintaining a real-time characteristic since the access request contained in the tasks are divided into partial request units by the access-request mediating portion to switch the access requests.

Abstract: In order to increase concealment of stored data without causing decryption-key management to become complicated, data blocks stored in a memory include execution blocks and decryption information sets. The execution blocks are obtained by dividing an original program into data sets, and then encrypting the divided data sets with respectively different key data sets. The decryption information sets include encrypted key data sets, each of which is used to decrypt the data block that will be read subsequently. When each data block is read into a microcomputer, the encrypted key data included in the decryption information is decrypted by a decryption portion, and then retained in a key-data temporary retention portion, before it is retained in a key data retention portion when the subsequent data block is read. The decrypted and retained key data decrypts the decryption information and execution block included in the next data block.