| 摘要 |
An interface circuit for a printer to prevent transmission of an incorrect control signal when power is input into the printer. The interface circuit improves the stability of the printer at the initial state of the rise of power supply voltages, and prevents erroneous operation. After power is input, in a switching control part 110, a flip-flop X23 is reset, a level change of output signals s1-s5 of an input part 100 is detected by a NAND gate X21, and an output signal s9 of the flip-flop X23 is raised. In a switching part 120, when the signal s9 is at low level, output signals s10-s14 are held at high level, and when the signal s9 is at high level, the output signals s1-s5 of the input part 100 are output to an output part 130. Thus, the output signals are held after the power input, and after the input signal rises, the signal transfer function is started, so that the output of incorrect control signals can be prevented, and thereby erroneous operation of a printer can be prevented.
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