Method and apparatus for bi-directional bus driver

DETAILED DESCRIPTION The present invention provides a self-directioning bidirectional bus circuit that can sense the direction of bus signals and drive bus lines in the direction of the bus signals.
A bidirectional bus circuit according to the present invention typically includes: (a) a first and a second bus line portion for carrying a bidirectional bus signal, where the first bus line portion has a first and a second end, and the second bus line portion has a third and a fourth end; (b) a bus direction sense line for carrying a bus direction signal; (c) a sensing circuit coupled to the sense line for detecting the bus direction signal; and (d) a driving circuit coupled to the sensing circuit and coupled between the second end of the first bus line portion and the third end of the second bus line portion for driving the first and second bus line portions.
According to one embodiment of the present invention, the sensing circuit may include: (a) a first NAND gate having a first and a second sense input line and a first sense output line, where the first sense input line is coupled to the bus direction sense line, and the first sense output line is coupled to the driving circuit; and (b) a second NAND gate having a third and a fourth sense input line and a second sense output line, where the third sense input line is coupled to the bus direction sense line, the fourth sense input line is coupled to the first sense output line, and the second sense output line is coupled to the second sense input line and to the driving circuit.
It should be noted that instead of having the NAND gates, the sensing circuit may include two NOR gates.
The sensing circuit may be coupled to other driving circuits that are in series with the driving circuit mentioned above.
Also, the sensing circuit may be coupled to other driving circuits that are in parallel with the driving circuit mentioned above as long as the bus signals along their respective bus line portions travel in the same direction at a given time