| 摘要 |
PURPOSE:To control an external storage device even in a small scale information device making unnecessary an extending I/O port which is installed as a separate parts by connecting an address bus for the external storage device sharing a port for a key scanning. CONSTITUTION:A key matrix 2 and a RAM 3 are connected to an information processor 1, but at such a case, ports P10, P11,... for the key scanning at the information processor 1 are shared. And a bus 7 which shares a bus outputting a key scan signal and the bus outputting an address signal to the RAM 3 is connected to the ports P10, P11,.... These ports P10, P11,... have no relation with the RAM 3 because they output data for the key scanning in an ordinary state. When the RAM 3 is accessed, the address of the RAM 3 is outputted, and a read/write for the RAM 3 can be performed. Therefore, no extending port installed as the separate parts is required.
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