| 摘要 |
PURPOSE:To prevent the adverse effect to be produced at checking, by disconnecting all other data communication controllers from a bus by a diagnosis setting command, in a system connecting plural data communication controllers to buses. CONSTITUTION:A diagnosis set command line 106 and a diagnostic address line 107 are provided in addition to a normal communication bus 105. The diagnosis setting command line 106 is brought into a high level by a command 108 of the diagnostic command from a central processing unit 101 in executing the diagnosis and all other data communication controllers 102 are disconnected from the communication bus 105. Then, a command address pulse from a data communication controller 100 of the diagnosis side is transmitted to the diagnostic address line 107 and the controller to be commanded only is connected to the communication bus 105. Thus, the adverse effect on the communication bus is eliminated and the checking of a specific data communication controller is performed. |
