The transmit/receive (T/R) input determines the direction of data flow through these bidirectional transceivers. Transmit (active high) enables data from A ports to B ports. The output enable (OE), when high, disables both the A and B ports by putting them in the high-impedance state. These devices are fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs, preventing damaging current backflow through the device when it is powered down.