Usually more complex digital circuits have a datapath circuit, which is used store and manipulate data, and a control circuit (usually implemented via finite state machines), that controls the operation of the datapath circuit. A bus (barramento) is a structure that can interconect multiple parts of a circuit using the same set of wires. Bus structures create a common path to transfer data from multiple sources to multiple destinations, for that reason it’s necessary to ensure that only one source is active at a time, to prevent interference.
Tri-state drivers
Tri-state drivers are simple buffers that can propagate the sign of the input to the output, without performing any logic operation. The idea here is that these drivers recieve a enable signal, that allows us to disable the connection when needed. When the connection is disabled, the output enters in a high impedance state, that is denoted by the letter (or ).
This type of connection allows us to control which connections will be active in the bus. A circuit using a bus that implements this tri-state drivers idea can look like that:
Multiplexers
We can also control the connections on the bus using multiplexers to select which source of data will be active.
