Discrete Logic is a term that refers to logic circuits that are made almost entirely of discrete logic devices such as AND and ORs (or their complements NAND and NORs). While it can be said that any digital system is made of basic logic gates, this term is reserved for systems that are primarily made of individual discrete components such as resistors, capacitors, such chips and single-functionality chips such as those provided by the 7400 series.
Likewise, a discrete logic chip is integrated circuit that performs a single function such as ANDing or XORing two inputs. An example of such chip is the 7404 hex inverter – an IC that contains 6 individual inverters. This is contrast with complex ICs such as microprocessors and microcontrollers.
A chip that contains one logic gate or a small number of logic gates. Although thousands of gates are routinely placed on a single chip, discrete-logic chips with only one or two gates are also manufactured. These chips are used as “glue chips” between ASICs and other ICs typically to reshape and transfer signals.