| 摘要 |
PURPOSE:To mount easily a RAM in a controller by providing a discriminating circuit and a transfer direction determining circuit which judge and determine the transfer direction of data and a read/write circuit which transfers data according to the determination. CONSTITUTION:A control signal regarding the direction of data transfer from a host system 4 is inputted to the read/write discriminating circuit 6 of the controller 2. The circuit 6 when discriminating data transfer from an IC3 to the RAM5 informs the data transfer direction determining circuit 7 of that, which decides that the request to the RAM5 is a write instruction. Consequently, the data transfer direction is determined and sent to the read/write circuit 8. Consequently, data read from a driver 1 by the IC3 is written in the RAM5. Then, when a request for transfer from the system 4 is generated, data from the RAM5 is transferred to the system 4 according to the decision results of the circuits 6 and 7.
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