Parallel Port Interface:
The parallel port is a 25 pin connector on your computer that is commonly known as the printer port, LPT1 or LPT2. This port is nice because it is relatively easy to manipulate it with software and the data is transmitted using standard TTL 0 – 5V signals. Another pro to using this port is there is no need for additional hardware to put the signal back together so that it can be loaded into the microcontroller.
The one major drawback for our project is that the parallel port hogs up a lot of pins and that can be a problem when you’re dealing with a 16 pin microcontroller. To utilize the parallel interface we would need 8 pins for the data transmission, 1 pin is an IRQ which signals that the data is ready and clocks it through, 1 pin to signal whether the data transmission was an address or actual data because we are employing multiple microcontrollers, and 1 pin to send a signal back to the PC telling it that the current task has been accomplished and it is ready for the next instruction.