| 摘要 |
PURPOSE:To prevent an erroneous setting by providing an automatic device number setting circuit on an input/output controller, and also, cascading each input/output controller in accordance with a prescribed sequence. CONSTITUTION:An automatic device number setting circuit 507 identifies whether a signal line 6 from a pre-positioned input/output controller 5 is connected or not. When the signal line 6 from the pre-positioned input/output controller 5 is connected, the automatic device number setting circuit 507 counts a number setting pulse transferred from the pre-positioned input/output controller 5 through the signal line 6, sets a device number, based on its counting value, and also, sends out the number setting pulse which is subtracted one pulse from the number setting pulse transferred from the pre-positioned input/output controller 5, to the number setting signal line 6 which reaches the post-position. In such a way, the device number of each input/output controller 5 connected to an input/output bus 4 is set automatically, and an erroneous setting caused by an operation error, etc. is prevented.
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