Scan path forming circuit

摘要

A connection circuit (CC) is formed by selectors (2,3) and a flip-flop (4). Th selectors (2,3) are switch-controlled by a test holding control signal (thld) and a shift mode control signal (sm) respectively. A scan-in terminal (si) is connected to a data input 0 terminal of the selector (2), while an output terminal of the flip-flop (4) is connected to its data input 1 terminal. An output terminal of the selector (2) is connected to a data input 1 terminal of the selector (3). An input terminal (d) is connected to a data input 0 terminal of the selector (3). An output terminal of the selector (3) is connected to an input terminal of the flip-flop (4). The output terminal of the flip-flop (4) is also connected to a scan-out terminal (so) and an output terminal (q) of the connection circuit (CC). In an ordinary operation, data is inputted through the input terminal (d). Thus, a scan path forming circuit attaining a high-speed operation in an ordinary operation is provided.