PC Hardware in a Nutshell, 3rd Edition

PC-to-peripheral parallel cables

It used to be that a printer cable was a printer cable. Not anymore. Printer cables now come in a variety of types, which use different connectors and pinouts. The good news is that you can still use any printer cable to connect a PC to a printer—as long as the connectors physically fit—and that connection will work in some fashion. The bad news is that using an old printer cable may cripple the performance and functionality of the link.

When you buy a new parallel cable—which you should if you are now using an older cable to connect a recent port to a recent peripheral—make sure it’s labeled “IEEE-1284-1994 Compliant.” Table 23-1 through Table 23-4 show the pin connections for the standard IEEE-1284 cables you are likely to need. To ensure optimum parallel performance, use an IEEE-1284 cable with connectors appropriate for your PC parallel port and the peripheral to be connected.

Table 23-1 shows the pinouts for a standard SPP 25-wire Centronics C36M-to-DB25M parallel printer cable, including signal polarities and directions. The missing C36M pins are not connected. The original IBM Parallel Cable and some inexpensive currently available cables use only 18 wires, using a single wire to tie DB25M pins 18 through 25 to C36M pins 19 through 30 and 33. These 18-wire cables may not work in all applications, notably with OS/2.

Table 23-1. The pinouts for a standard SPP 25-wire Centronics C36M-to-DB25M parallel printer cable

C36M	DB25M	Description