This 16-bit registered transceiver is designed for 1.65-V to 3.6-V VCC operation. The SN74LVCH16543A can be used as two 8-bit transceivers or one 16-bit transceiver. Separate latch-enable (LEAB\ or LEBA\) and output-enable (OEAB\ or OEBA\) inputs are provided for each register, to permit independent control in either direction of data flow. The A-to-B enable (CEAB\) input must be low to enter data from A or to output data from B. If CEAB\ is low and LEAB is low, the A-to-B latches are transparent; a subsequent low-to-high transition of LEAB\ puts the A latches in the storage mode. With CEAB\ and OEAB\ both low, the 3-state B outputs are active and reflect the data present at the output of the A latches. Data flow from B to A is similar, but requires using the CEBA\, LEBA\, and OEBA\ inputs. To ensure the high-impedance state during power up or power down, OE\ should be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver. Inputs can be driven from either 3.3-V or 5-V devices. This feature allows the use of these devices as translators in a mixed 3.3-V/5-V system environment. This device is 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. Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level. Use of pullup or pulldown resistors with the bus-hold circuitry is not recommended. The bus-hold circuitry is part of the input circuit and is not disabled by OE\ or DIR.