| 摘要 |
PURPOSE:To perform a diagnosis and a device scanning operation with good efficiency by a method wherein an additive logic is added to a bit-serial scanning circuit and a scanning-system changeover signal is input. CONSTITUTION:A signal input S and additive circuits 101 to 103 which function as a selection logic are added to, and constituted in, a serial scanning circuit. The additive circuit 101 is provider with a constitution which performs a logic operation for a signal from the signal input S and for an address signal by means of an OR gate. For example, when a signal indicated by 0 out of outputs from an address decoder 104 is set at a high level, a state that flip-flops B0, B1 are selected simultaneously is set and data can be written and read out simultaneously. The additive circuits 102, 103 perform a logic operation for signals of ordinary logic pins I, O as pins which input and output data and for the signal input S with reference to flip-flops B1, B2. When the signal input S is set at a high level, the ordinary logic pins can be used to input/output data on a scanning operation. When the signal input S is set at a low level, an address signal and an ordinary logic are not affected. As a result, the same logic function as an ordinary bit-serial scanning circuit can be realized. |
