# Parallel port loop back plug

(Applicable to BurnInTest Pro version only)

You can purchase high quality molded loop back plugs from PassMark or you can make your own. You'll find below the instructions for making a parallel port loop back plug. These plugs are designed to be plugged into the 25 pin parallel on your computer. In conjunction with software such as BurnInTest they allow the testing of the port.

Warning: This are the pin outs of the plug which we have made and successfully tested with our own software on our own PC's. You use this information at your own risk! It's easy to make a mistake and we take no responsibility for the potentially serious consequences.

The parallel port on IBM compatible PC's have always used a DB-25 connector. However, over time several changes have taken place to the electrical interface with the introduction of enhanced and bi-directional parallel ports. We believe that this plug will work with all styles of parallel ports.

DB-25 Pin | Direction | Description
2 | Out | Data bit 0 (Least significant bit)
3 | Out | Data bit 1
4 | Out | Data bit 2
5 | Out | Data bit 3
6 | Out | Data bit 4
10 | In | Acknowledge status
11 | In | Busy status
12 | In | Paper out status
13 | In | Select status
15 | In | Error status

To make the loop back plug the following pins need to be connected together

- Data 0 and Error status (Pin 2 & 15)
- Data 1 and Select status (3 & 13)
- Data 2 and Paper out status (4 & 12)
- Data 3 and Acknowledge status (5 & 10)
- Data 4 and Busy status (6 & 11)

This diagram shows the connections that need to be made. It's the rear view of the male DB-25 connector that's required for the plug. The red lines and grey dots show the connections that need to be made.

Male DB-25 connector - Rear view