| 摘要 |
PURPOSE:To easily expand the program capacity, by using a signal selecting means that delivers an output only when the selection signal is received plus a decoding means that decodes the address designating signal and then gives an access to a storage part. CONSTITUTION:In case a connection is given as shown by the solid lines in the diagram to a switch panel 22 for an expanding board of program region, the corresponding board is selected when the board selection signals of 1, 0 and 0 are applied to BS0, BS1 and BS2 respectively. Then the board selection signals to the NAND gate via an AND II gate. The output of the gate NAND is set at 0 when the higher two bits are set at 1 and 0, i.e., the highest digit of the 16-notation code is >=8 of address designating signals A15-A0 and at the same time the board selection signals BS0-BS2 of 1, 0 and 0 are applied. Then the terminal D of a decoder 21 is set at a low level. In this case, the programs of memories M0-M2 are read out via output lines D0-D7 if these memories are ROMs. |
