| 摘要 |
PURPOSE:To make the increase in the dedicated testing circuits of a circuit board as small as possible even if the number of input/output terminals is increased by providing a control circuit, which can switch an actually operating signal and a test signal, and sharing the actual operating logic and a circuit- board testing circuit. CONSTITUTION:Multiplexers 2a and 2b for selecting an actually operating signal and test data signals T1 and T2 of an actual operation logic part 6 are provided at the data input parts of flip-flops 4a and 4b for input terminals IN1 and IN2. In the clock input part, multiplexers 3a and 3B for selecting the actually operating signal of the actual operation logic part 6 and a test clock signal CK, which is inputted from a test clock terminal SCK, are provided. The flip- flops can be shared with a circuit-board testing circuit by providing a control circuit, which switches the actually operating signal and the test signal, and the dedicated flip-flop for the test is not required. |
