The 74HC574PW is a 8-bit positive-edge triggered D-type Flip-flop with 3-state outputs. The device features a clock and OE\ inputs. The flip-flops will store the state of their individual D-inputs that meet the set-up and hold time requirements on the low-to-high clock transition. A high on OE\ causes the outputs to assume a high-impedance OFF-state. Operation of the OE\ input does not affect the state of the flip-flops. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.
The SN74HC574PWR is an octal edge-triggered D-type Flip-flop with 3-state outputs. It is designed specifically for bus driving. They are particularly suitable for implementing buffer registers, I/O ports, bidirectional bus drivers and working registers. The eight flip-flops enter data on the low-to-high transition of the clock (CLK) input. 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 interface or pull-up components. OE\ does not affect the 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.