| 摘要 |
PURPOSE:To prevent overflow of a memory, by monitoring an address distance of write and read-out, and lowering a clock of write and read-out when its value becomes below a prescribed value. CONSTITUTION:Information from a write address counter 5 and information from a read-out address counter 7 are supplied to a subtracter 10, and a difference of both address information is supplied to one input terminal of comparators 11, 12, comparing reference voltage E1 and E2 are supplied to the other input terminal, and for instance, they are made E1>E2. Outputs of the comparators 11, 12 are supplied to a control signal generator 13, and by its output, output clock frequency of a write clock generator 4 and a read-out clock generator 6 are controlled. When an output difference of the subtracter 10 becomes smaller than a prescribed value, namely, when it is feared that a memory 3 overflows, write and read-out clock frequencies are lowered simultaneously so that capacity of the memory 3 increases substantially in appearance. In this way, overflow of the memory can be prevented. |
