| 摘要 |
PURPOSE:To simplify the circuit constitution by storing the specific key codes to the memory parts of both basic and optional function programs respectively and discriminating the presence or absence of the optional function in response to the presence or absence of the specific key codes when they are read out. CONSTITUTION:The basic function program is stored to ROM1-ROMn-1 respectively, and an optional program is stored to an ROMn. The specific key codes X of plural digits are stored to the prescribed addresses of a basic function program, e.g. ROM2 and the optional function program. Then a device is started to read the key codes of the ROMn and the ROM2, and then the optional function program is set when the coincidence is obtained between both ROMs. While no optional program is set and the initialization is carried out when no coincidence is obtained between both ROMs. Then processes A-D are carried out by the basic function program. When no optional program is available, the process A is reset; while processes E-G are carried out by the optional program and then the process A is reset when the optional program is available. Thus the change is facilitated for loading/unloading of optional program. This system is suitably applied to a vending machine.
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