DRAM CONTROLLER AND CONTROL METHOD

摘要

PROBLEM TO BE SOLVED: To reduce the number of required DRAMs at the time of reading data from the plural DRAMs by an interleave system in real time. SOLUTION: The (n+m) DRAMs and a selection control means for selecting and controlling the DRAM for performing read and the DRAM for performing refresh among the (n+m) DRAMs are provided. For the (n+m) DRAMs, an integer equal to or more than the quotient for which the read time of one DRAM is divided by desired read cycle time by interleave is defined as n and the integer m is determined so as to make the product of the ratio of the time of being in a readable state in a refresh cycle for one DRAM and the number (n+m) of the DRAMs be n or more. The selection and control means successively turns the m DRAMs to a refresh state at a time and turns the remaining n DRAMs to the readable state during the time.