| 摘要 |
PURPOSE:To contrive the diagnosis of an adder by providing the input selecting circuits to both inputs of the adder for test of this adder and supplying the output of a counter to said both inputs of the adder to perform comparison between the output of the adder and the value obtained by doubling the output of counter. CONSTITUTION:Both selecting circuits 21 and 22 are switched to check whether an adder has a trouble or not while the adder 5 is not used. Thus the output of a counter 1 is sent to both inputs of the adder 5. The output of the counter 1 is doubled and delivered through a 1-bit left shifter 3. Here the output of the adder 5 must be double as much as the output of the counter 1 as long as the working of the adder 5 is normal. Then the output of the adder 5 must be equal to the output of the shifter 3. Thus it is possible to diagnose the adder 5 by comparing both outputs of the adder 5 and the shifter 3 through a comparator 4. The counter 1 is actuated by the clock that is used also for the actuation of the adder 5. |
