| 摘要 |
PURPOSE:To detect the fault position of a scan path by outputting data from a specific position of the scan path through an external output terminal in scan mode. CONSTITUTION:A mode switching signal is held at the level of logic 1 to set a scan mode, and data are set in FFs 2a-2d. Then the mode switching signal is held at the level of logic 0 to switch the mode to a normal operation mode and then a selector 3c allows its input-side data to be transferred to its output side, when a clock signal is set in the Ffs 2a-2d, the contents of the data set in the Ffs 2a-2d vary according to the specific processing of a scan design circuit in normal operation mode. The mode switching signal is held at the level of logic 1 again to set the scan mode, and the clock signal is applied to the FFs 2a-2d to scan the data out and outputted data from the FFs 2a and 2b from an output terminal P0 through a NAND gate 1c and an inverter 1b. Then the scanned-out data and output data from a terminal P0 are used to detect the fault position of the scan path. |
