JPS5690359A - Information control unit - Google Patents

Abstract

PURPOSE: To protect memory information of a memory device, by providing the function for confirming the correctness of the memory address to be accessed, in case of transferring the information to the memory device.

CONSTITUTION: The precedence is given to the transfer request 21 from each device, and the transfer type designation 22, by the priority circuit 10. The highest precedence transfer request 27 and its transfer type designation 26 become indexes of the memory part 12. The memory part 12 consists of an effective fit part 41, a relative address designation part 42 and an address part 43, which output an effective bit 32, a relative address designation 33 and an address 34, respectively. The comparator 13 compares the output addresses 31, 34 of the selecting circuit 11 and the memory part 12 in accordance with the instruction of the bit 32 and the address designation 33, and in case of coincidence of the compared results, a coincidence signal 36 is output. The output of the NAND circuit 14 which inputs the effective bit 32 becomes an approval signal 41 together with the signal 36, by the OR circuit 15. The transfer request 27 to which the precedence has been given by the circuit 10 requests a memory access 42 through the AND circuit 16 only when the signal 41 has shown the approval state.

COPYRIGHT: (C)1981,JPO&Japio