| 摘要 |
PURPOSE:To obtain a ROM circuit capable of selecting a ROM or a RAM with easy switch operation, by providing a ROM/RAM switch which corresponds to a selected ROM or RAM, and a ROM switch and a RAM switch which correspond to respective capacity. CONSTITUTION:When an address signal A14 is inputted to the upper side of a central terminal, and the earth potential to the lower side by the operation of the ROM/RAM switch 2, an enable signal goes to (0), and the output sides of three-state buffers 5 and 6 go to high impedance states and a three-state buffer 7 outputs a W signal. Consequently, the W signal is inputted to the terminal T3 whose terminal number is 27 in a memory IC1, and the address signal A14 is inputted to the terminal T1 whose terminal number is 1, then, the RAMs corresponding to those numbers are selected. Next, when a static RAM (SRAM) having specific capacity is selected, an address signal A13 is inputted to a terminal T2 by the operation of a RAM capacity switch 3, thereby, the SRAM having a corresponding capacity can be selected.
|
