| 摘要 |
PURPOSE:To reduce the activity ratio of a bus by selecting a required inseparable read/write signal out of signals outputted from a processor, and making perform a bus access. CONSTITUTION:When a reference to a storage device in which an inseparable readout/write signal 5 is at a level of 1 is generated, an address 7 and a data 8 at that time are stored at registers 28 and 29 respectively, and an FF22 is set at the level of 1. And at every reference to the storage device by a processor 1, an address is compared with the previous one stored at the register 28, and when they coincide with each other, a bus request signal 32 is set at a level of 0, thereby preventing a bus operation from being generated, and also, the data 8 at the register 29 is returned to the processor 1 as a result read out from the storage device. Meanwhile, by detecting a coincidence between the address signal 7 on a bus 2 and the address in the register 28 at a comparator 33, and detecting both that it is a write operation, and that it is not an inseparable signal by an AND gate 34, the FF22 is reset through an OR gate 21.
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