DRAM REFRESH SYNCHRONOUS TYPE MEMORY DOUBLING DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent a refreshing process from becoming out of synchronism even at system switching time by allowing a refresh request generation part of an in-operation system common memory card to send a refresh synchronizing signal to a refresh request part of a stand-by system common memory card only when the card is initialized. SOLUTION: When an other-system initialization completion signal is received within a prescribed time, clocking is ended, it is judged that this system is an in-operation system and there is the other system (standby system), and a refresh synchronous responding circuit 24 is informed of a refresh generation request and a state 17 and sends an external refresh synchronizing signal 15-o to the other system. The refresh synchronous responding circuit 24 which is informed of the request sends of a refresh counter clear request signal 26 to a refresh counter control circuit 23. A refresh counter 25 counts thereafter in synchronism with a bus clock and sends a refresh request signal 18 out to a memory access arbitrating circuit in fixed cycles.