| 摘要 |
PURPOSE:To eliminate the need for a resistor connected externally by holding the state of a two-way terminal and keeping the state of a bus line just before when outputs connected to a bus line go all to high impedance so as to prevent the bus line from going to an uncertain level. CONSTITUTION:An output of the 1st, 2nd tri-state circuits 1, 2 is connected respectively by a signal line 12 and to an input of an input circuit 3. When the level of a control signal 10 is logical ''1'', the 1st tri-state output circuit 1 outputs its data input signal 13 and an output of the 2nd tri-state output circuit 2 goes to high impedance state in this circuit. When the control signal 10 is logical ''0'', an output of the 1st tri-state output circuit 1 goes to high impedance state, and the state of the two-way terminal 5 of an integrated circuit just state is held via the input circuit 3 and the 2nd tri-state output circuit 2. Thus, the input state of the input circuit 3 is logical ''1'' or ''0'' at all times and does not go to the uncertain state. |
