| 摘要 |
PURPOSE:To prevent a malfuncion caused by disturbance by setting a flag when an input/output port is in an input mode, outputting an OR output with an output latch through an output driver, and outputting an abnormality signal when the output latch and a value of the flag are different each other. CONSTITUTION:Plural output data 1 are latched to an output latch 2 by a latch clock 3, and a level 1 is written. An input mode flag 10 is set to the level 1 by an input mode setting signal 11. The latch 2 and the flag 10 output ''1'', it becomes an input data signal 6 through an OR circuit 13 and an output driver 4, and it is sent into a data bus which is not shown in the figure. When the input mode flag is ''1'', if at least one of the output latches 2 is reduced to ''0'', an input mode abnormality detecting part 14 output 15 an abnormality signal. By this abnormaity signal, an interruption is applied to a mu computer, and a reset processing program from a fault is executed. In this way, a malfunction caused by disturbance, etc. of an input/output circuit of the mu computer can be reduced easily. |
