These devices can be used as two 8-bit transceivers or one 16-bit transceiver. They allow data transmission from the A bus to the B bus or from the B bus to the A bus, depending on the logic level at the direction-control (DIR) input. The output-enable (OE ) input can be used to disable the devices so that the buses are effectively isolated. Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended. When V is between 0 and 1.5 V, the devices are in the high-impedance state during power up or power down. CC However, to ensure the high-impedance state above 1.5 V, OE should be tied to V through a pullup resistor; CC the minimum value of the resistor is determined by the current-sinking capability of the driver. and power-up 3-state. The I circuitry These devices are fully specified for hot-insertion applications using I off off disables the outputs, preventing damaging current backflow through the devices when they are powered down. The power-up 3-state circuitry places the outputs in the high-impedance state during power up and power down, which prevents driver conflict.