How to Read LPT1 Port Pins

LPT1 ports typically connect computers to devices such as printers.

According to the Institute of Electrical and Electronics Engineers, the LPT1, or parallel port, is a bidirectional communication link between a personal computer and a peripheral device, such as a printer. Each LPT1 is recognizable by having a female component -- a port with a set of set of 25 pin holes, which can be found on the back of a computer -- that connects to a male attachment, which has 25 pins and is usually found on the end of a connecting cable. Visually the outline of the port will resemble a trapazoid. Each LPT1 pin has a specific function that allows the computer to communicate with the peripheral device. Labeling the LPT1 pins can make it possible to read the pins correctly every time.

Things You'll Need

• D-25 type female LPT1 port
• D-25 type male LPT1 connector cable

Instructions

Reading an LPT1 Port Male Connector

1. Locate the D-25 type LPT1 male connector on the end of the parallel cable. It should look identical in shape to the female port, except the male connector has pins instead of pin holes. Rotate the male connector until it is horizontal and the longer row of pins is on top.

2. Locate the starting pin along the longer side of the male connector's row of pins. The starting pin is the pin farthest to the left on the top row. Label this as pin number 1.

3. Read from left to right across the top row to number the remaining pins in that row. The labels across the top row of pins should run from 1 to 13, with the 13th pin being the last pin on the right.

4. Label the bottom row of pins, beginning with the pin farthest to the left. Label this as pin number 14.

5. Read from left to right across the bottom row of pins to number the remaining pins in that row. The labels for the bottom row of pins should go from 14 to 25, with the 25th pin being the pin farthest to the right.

Reading an LPT1 Female Port

1. Locate the D-25 type LPT1 female connector port on the back of the computer. Position the computer on its side so that the port is horizontal, and the longer of the two rows of pin holes is on top.

2. Locate the starting pin hole along the longer row of pin holes. With the port horizontal and the longer side on top, the starting pin hole will be at the right corner of the top row. Label this as pin hole number 1.

3. Read from right to left across the top row to number the remaining pin holes in that row. The labels of the top row of pin holes should go from 1 to 13, with the 13th pin hole being the last one on the left side.

4. Label the bottom row of pin holes, beginning with the pin hole farthest to the right. Label this as pin hole number 14.

5. Read right to left across the bottom row of pin holes to number the remaining holes in that row. The labels of the bottom row of pin holes should run from 14 to 25, with the 25th pin hole being the last one on the left.

References

• Institute of Electrical and Electronics Engineers: 1284-1994 -- IEEE Standard Signaling Method
• Electrosofts: Parallel Port Programing (Part 1): With C