The HD74ALVCH16543 can be used as two 8-bit transceivers or one 16-bit transceiver. Separate latch enable (LEAB or L EBA ) and output enable (OEAB or O EBA ) 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 in order to enter data from A or to output data from B. If CEAB is low and L EAB 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 CEBA , LEBA, and OEBA. Active bus hold circuitry is provided to hold unused or floating data inputs at a valid logic level.