Octal Registered Transceivers with 3-State Outputs and Series Damping Resistors

The CY74FCT2543T octal latched transceiver contains two sets of eight D-type latches. Separate latch enable (LEAB\, LEBA\) and output enable (OEAB\, OEBA\) inputs permit each latch set to have independent control of inputting and outputting in either direction of data flow. For example, for data flow from A to B, the A-to-B enable (CEAB\) input must be low to enter data from A or to take data from B, as indicated in the function table. With CEAB\ low, a low signal on the A-to-B latch enable (LEAB\) input makes the A-to-B latches transparent; a subsequent low-to-high transition of LEAB\ puts the A latches in the storage mode and their outputs no longer change with the A inputs. With CEAB\ and OEAB\ both low, the 3-state B output buffers are active and reflect data present at the output of the A latches. Control of data from B to A is similar, but uses CEAB\, LEAB\, and OEAB\ inputs. On-chip termination resistors at the outputs reduce system noise caused by reflections. The CY74FCT2543T can replace the CY74FCT543T to reduce noise in an existing design.

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.