Interfacing PIC Microcontrollers

USB is that it provides a simple, robust connector and this outweighs the fact

that the interface protocol (driver software) is relatively complex, because this

is hidden from the user. USB also provides power to the peripheral, if required,

and the printer can be daisy-chained with other devices. USB also automati-

cally configures itself for different peripherals, such as scanners and cameras.

In the parallel port operating in output mode, the data byte is loaded from the

internal data bus under the control of a read/write signal from the CPU. The

data can then be seen on the output pins by the peripheral; for testing, a logic

probe, logic analyser ...