The 'BCT543 octal transceiver contains two sets of D-type latches for temporary storage of data flowing in either direction. 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 in order 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.
The SN54BCT543 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74BCT543 is characterized for operation from 0°C to 70°C.