| 摘要 |
PURPOSE:To write even such a program that requires a capacity larger than an address space of an MPU into plural ROMs by providing a means which decodes the address of the MPU, a means which switches the selection signals of the ROM with said decoded address and plural ROMs connected to the same address. CONSTITUTION:A program is read out of an address Yb of a ROM 11 while another program is executed in an address Xa. In such a case, the addresses Ya of ROM 10 and 11 are called in an address Xa of a ROM 9 or 10 and therefore the SCSS signal is outputted from a decoding means 3. Then a CS2 signal is outputted from a decoding means 2. Thus the ROM 11 is selected. The instructions which call the address Yb is written to the addresses Ya-(Ya+2) and the same instructions are written into the addresses Ya(Ya+2) of the ROM 10 and the addresses Ya-(Ya+2) of the ROM 11 respectively. Thus the address (Ya+1) of the ROM 11 and the program of the address (Ya+2) are read out after the address Ya of the ROM 10. Then the addresses Yb are called and carried out successively.
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