| 摘要 |
PURPOSE:To enable ROM for control to be fixed to an optional position by adding an address conversion function to a decoding circuit for decoding an address high in hierarchy fed from a microprocessor and selecting one from plural control ROM. CONSTITUTION:The common buses of a microcomputer 10 are shown as an address bus 11 and a data bus 12, the group of bits of the bus 11 lower in hierarchy designates the addresses of ROM 13-16 for storing a control program, and the group of bits higher in hierarchy is used as the selection signals 20 provided to an ROM address converter 17 for selecting the chips of ROM 13-16. The bus 12 is used as a readout data signal provided from ROM 13-16. The address setting information 19 of an input and output port 18 is used as another selection signal of the converter 17, and one is selected from ROM 13-16 in accordance with the information 19 together with the higher bit group information of the bus 11. As a result, the control ROM can be used by attaching it to an optional position. |
