JPS57197645A - Data transfer control device - Google Patents

Abstract

PURPOSE:To eliminate unnecessary data transfer and improve the efficiency of the use of a system by implementing transfer operation only in the case of requesting for data transfer that is different from the previous one referring to the address data stored in reference memory. CONSTITUTION:As to reference memory that stores an address of (a) transfer data, for instance, it inputs an address data to multiplexers 10 and 11 through an address bus 9, and based on a select signal outputted by a dynamic memory access controller DMCA 5, writes data (f) and (g) in the same contents as the address data in reference memory 12 and 13. Then, if there is a request for transfer from a CPU 3, it stores a transfer display data ''1'' in the address assigned by the address data (f) and (g), and outputs update data (h) and (i) which becomes ''1'' only when a request for transfer is made for a different address by the reference memory 12 and 13, and sends them to a selector 14. Then, it outputs the signal selected by the selector 14 to the DMCA 5 as a read signal (j).