| 摘要 |
PURPOSE:To ensure an effective application of a memory, by installing a means to switch the control between the ROM and RAM and thus carrying out a writing-in to the RAM for the area where the ROM overlaps the address region along with a selective reading-out given to both memories. CONSTITUTION:The switching means 5 switches the control between the ROM3 which stores a program and the RAM4 which also functions as a data buffer. The writing-in is given to the RAM4 for the area where the ROM3 overlaps the address region; and the reading-out is carried out selectively to both the ROM3 and RAM4 and in accordance with the set and reset states, respectively. For instance, the switching circuit 5 is provided as shown in the diagram to give the reset signal from the control part 1 via the signal lines 11-13. Thus the memory is read through the ROM using region 3-0; while a memory reading is carried out through the RAM ineffective region 4-2 when the set signal is applied through the signal line 10. |
