These octal buffers and line drivers are designed to have the performance of the HCT240 devices and a pinout with inputs and outputs on opposite sides of the package. This arrangement greatly facilitates printed circuit board layout.
The 3-state control gate is a 2-input NOR. If either output-enable (OE1\ or OE2\) input is high, all eight outputs are in the high-impedance state. The HCT540 devices provide inverted data at the outputs.
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.