What this 74HC inverting buffer does on your board
The SN74HC540NSR: It takes eight input signals and presents their inverted logic levels on the outputs, with a single output-enable (OE) pin that puts all outputs into a high-impedance state for bus isolation or shared-line arbitration.
Output drive and bus isolation
Each output sources or sinks 7.8 mA (symmetric high/low), which is typical for 74HC and enough to drive CMOS logic inputs, LEDs with a series resistor, or short PCB traces. The 3-state outputs let you disconnect the buffer from a shared data bus or backplane without adding external bus switches — a single OE pin controls all eight channels.
Package and supply compatibility
Housed in a 20-SOIC (0.209", 5.30 mm width) surface-mount package. The 2V to 6V supply covers 3.3V and 5V rails without a level translator, and the 74HC family's CMOS inputs are 5V-tolerant at the higher supply end.