| 摘要 |
PURPOSE:To obtain a desired circuit scan ratio with high efficiency by attaining the scan for each circuit including a priority scan circuit and therefore securing a priority scan function and a scan skip function which are completly independent of each other. CONSTITUTION:In case two priority scan circuits exist together with four unused circuits, 28 and 416 pieces of signals exist on signal line groups S6 and S7 led from a scan mode register 1-5 respectively. Therefore the circuit scan time slots are given to circuits having circuit numbers 0 and 1 every time the priority scan slot value changes on a signal line groups S11. While the circuit scan time slot of a single time is given to a circuit in another using state every time the priority scan slot value makes a round. Thus no circuit scan time slot is sent to an unused circuit, As a result, the circuit scan ratio is set at 4 between the priority scan circuit and the circuit in another using state. At the same time, the scan is suppressed to the unused circuit. |
