2.12 Data Bus Operation

• Basic operation: one device has its outputs enabled so that its data are placed on the data bus; another device has its inputs enabled so that it can take these data off the bus and latch them into its internal circuitry on the appropriate clock edge
• A bus driver IC has tri-state outputs with a very low output impedance that can rapidly charge and discharge the bus capacitance
• This bus capacitance represents the cumulative effect of all the parasitic capacitance of different inputs and outputs tied to the bus, and can deteriorate the bus signal transition time if they are not driven from a low-impedance signal source.