Patent ID: 7535256

Claim:
A cross-level digital signal transmission device coupled between a first digital system and a second digital system having different ground levels and different voltage levels of high logic level and low logic level, comprising: a first gateway device having a first signal control terminal for conversion of a logic level of a first signal from the first digital system and transmission to the second digital system; a second gateway device having a second signal control terminal for conversion of a logic level of a second signal from the second digital system and transmission to the first digital system, wherein the first gateway device and the second gateway device connect in parallel and form a closed loop, the first gateway device controls the second signal control terminal when the first digital system transmits the first signal to prevent the first signal from transmitting to the first digital system by the second gateway device, and the second gateway device controls the first signal control terminal when the second digital system transmits the second signal to prevent the second signal from transmitting to the second digital system by the first gateway device; wherein the first gateway device comprises: a first logic level converter having the first signal control terminal for receiving the first signal and converting the logic level of the first signal; and a first delay device coupled between an output terminal of the first logic level converter and the second digital system and having the function of single-way transmission; wherein the second gateway device comprises: a second logic level converter, coupled to the output terminal of the first logic level converter, having the second signal control terminal, coupled to the first logic level converter, for receiving the first signal and converting the logic level of the first signal; and a second delay device coupled between an output terminal of the second logic level converter and the first digital system and having the function of single-way transmission; and wherein the first delay device outputs an output signal of the first logic level converter when the output signal of the first logic level converter turns off the second logic level converter by the second signal control terminal, and the second delay device outputs an output signal of the second logic level converter when the output signal of the second logic level converter turns off the first logic level converter by the first signal control terminal.