Step 1 : Conventions

A positive symbol (+) Indicates a PC Output (device input). A negative symbol (-) indicates a PC Input (device output).

Step 2 : The Standard Parallel Port (SPP/PS2)


1: +STROBE
2: +DATA0
3: +DATA1
4: +DATA2
5: +DATA3
6: +DATA4
7: +DATA5
8: +DATA6
9: +DATA7
10: -ACKNOWLEGE
11: -BUSY
12: -PAPER END
13: -SELECT
14: +AUTOFEED
15: -ERROR
16: +INIT
17: +SELECT IN
18-25: SIGNAL GROUND

IMAGE: 25 pin D-SUB female connector at the PC

Step 3 : Functions of the Parallel port

If a data bit (pins 2-9) has a 1 written to it, it will emit +5v (sometimes called "High"). A 0 written to a data bit will cause it to have virtually no emitions ("low").

The Control bits (pins 1,14, 16, 17) are opposite. A 1 written to it will produce a "low", while a 0 will produce a "high".