| 摘要 |
PURPOSE: A system for sensing an auxiliary unit using a ground signal is provided to connect a ground signal line of an auxiliary unit having an electronic circuit to a mount sensing signal line. CONSTITUTION: A connector(313) of an auxiliary unit(310) is connected to a connector(327) of a main unit(320), and supplies a power to the auxiliary unit(310) from a power supply unit(325) of the main unit(320). The auxiliary unit(310) connects a ground signal line of the connector(313) to a mount sensing signal line, and forms a loop connection(315). The main unit(320) connects the mount sensing signal line to a pull-up resistor(329) and a mount state sensing register(323). A main control processor(321) of the main unit(320) accesses to the mount state sensing register(323). Exchange of information between the main control processor(321) and the mount state sensing register(323) is executed by an address signal, a read signal, and a register selection signal in accordance with a register access, and a data signal for reading a state value. If the auxiliary unit(310) is not mounted or connected to the main unit(320), the mount sensing signal line maintains 'high" state by the pull-up resistor(329). If the auxiliary unit(310) is connected to the main unit(320), the mount sensing signal line transfers to 'low" state by the loop connection(315).
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