A simple latch has two stable logic states. The latch maintains its states indefinitely until an input pulse called a trigger is received. If a trigger is received, the latch outputs change states according to defined rules, and remain in those states until another trigger is received. Latches can be interconnected to form more sophisticated circuits that function in memory chips and microprocessors.
An octal latch can hold onto the data at its inputs before transmitting the data to its outputs. This ability is useful in applications where a number of devices share a single data bus, because it allows the processor to store data, go onto other operations that require the bus, and return to the stored data later if the need arises.
A common example of an octal latch is the Fairchild LVX573, an advanced high speed CMOS IC with eight three-state outputs. When the output enable input is high, the eight outputs are in a high-impedance condition.