| 摘要 |
PURPOSE:To control a memory circuit with simple constitution and a clear logic by connecting one of output lines in a selector group and (Nm-1) unused high-order address lines out of address lines to an input, and providing the m-th selector group having 2N<m> lines of output lines. CONSTITUTION:The output Y of a selector 1 is used as an input to a selector 2,and is used as a control line for a ROM area, and addresses 0-1FFF are used when a CPU reads out a program data from the ROM area. At such a time, assuming that an area can be constituted with five kinds of ROMs as the ROM area, and four ROMs of No.5 having 2,048 words X 8 bits are used, address lines ADB11 and ADB12 other than the output Y0 of the selector are required for the designation of addresses 0-1FFF, and these three lines are provided as the input to the selector 2. Next, assuming that an access memory of No.4 having 8,192 words X 8 bits is used as a RAM area, the outputs of Y1-Y3 in the selector 1 can be used as the control line. In this way, the control part of the memory circuit can be constituted easily, and universality is heightened.
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