SN74AHCT573-Q1,pdf(Octal Trans

The SN74AHCT573 is an octal transparent D-type latch. When the latch-enable (LE) input is high, the Q outputs follow the data (D) inputs. When LE is low, the Q outputs are latched at the logic levels of the D inputs.

A buffered output-enable (OE) input can be used to place the eight outputs in either a normal logic state (high or low) or the high-impedance state. In the high-impedance state, the outputs neither load nor drive the bus lines significantly. The high-impedance state and increased drive provide the capability to drive bus lines without interface or pullup components.

To ensure the high-impedance state during power up or power down,?OE?should be tied to V_CCthrough a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

OE?does not affect the internal operations of the latches. Old data can be retained or new data can be entered while the outputs are in the high-impedance state.