Octal Edge-Triggered D-Type Flip-Flops With 3-State Outputs

These octal edge-triggered D-type Flip-Flops SN74AC534 feature 3-state outputs designed specifically for driving highly capacitive or relatively low-impedance loads. The devices are particularly suitable for implementing Buffer Registers I/O ports, bidirectional bus drivers, and working Registers
On the positive transition of the Clock (CLK) input, the Q outputs are set to the complements of the Logic levels set up at the data (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 Logic levels) 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 need for Interface or pullup components.
OE does not affect internal operations of the Flip-Flops Old data CAN be retained or new data CAN be entered while the outputs are in the high-impedance state.
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.
By Texas Instruments