| 摘要 |
PURPOSE:To attain alternately bidirectional data transmission in insulating state without using a direction designating signal by bringing an optical transmission system in transfer direction into light emitting state by the input of an active true value data to bring the reverse direction into the non-transfer state. CONSTITUTION:When a signal of logical 0 is inputted to an input/output terminal I/O1, an output of a Schmitt inverter SI1 changes of 1, an input to an NAND gate G1 goes to 1 and the output is changed to 0. Thus, a light emitting diode of a photocoupler PC1 is lighted, a photo transistor (TR) is turned on, and the output goes to 1, then an output of an inverter SI4 goes to 0 and an output TR of an open collector buffer OC2 is turned on, then the output goes to 0, the same signal as that of the I/O1 appears at an input/output terminal I/O2 for attaining the data transfer. Since the output of the SI4 is changed into 0 in this case, the output of an NAND gate G2 remains logical 1 and the photo TR of the photocoupler PC2 is not lighted, an FF2 is set and the output is inverted. |
