What is Tri-state logic ?

Ans. Tri-state Logic:

In common logic circuits, there are two states of the output, as LOW and HIGH. If the output is not in the LOW state, this is absolutely in the other state that is HIGH. Likewise, if the output is not into the HIGH state, this is certainly in the LOW state. In complicated digital systems like microprocessors and microcomputers, a number of gate outputs might be essential to be linked to a common line which is referred to as a bus that in turn may be essential to drive a number of gate inputs.

While a number of gate outputs are connected to the bus, Totem pole TTL outputs leads to heating of the ICs that may find damaged and Open-collector TTL outputs causes the difficulties of loading and speed of operation.  To overcome these problems, as well as low impedance outputs 0 and 1, there is a third state termed as the High-impedance state. These logic circuits wherein the output can have three states are termed as tri-state logic.

In the Tri-state Logic, as well as low impedance outputs 0 and 1, there is a third state termed as the High-impedance state. While the gate is disabled, this is in the third state.