The computer checks the port by writing and reading data and control information, and reports errors for any pins that are faulty. Note that if you connect a printer cable instead of a loop-back connector, you get errors.

Parallel Port (on Video Adapter) Check

Use the Parallel port (on video adapter) check to test the functions of the primary port. This tests either the built-in port, if it is set up to act as the primary port, or the parallel port on a monochrome adapter (such as the IBM monochrome display and printer adapter) if you have one installed in your computer.

To perform the test, you must insert the special loop-back connector into the parallel port so that the computer can check the individual pins of the port. This test is identical to the Parallel port check. For more details, see the description of the Parallel port (printer interface) check above.

Serial Port (RS-232C) Check

Use this option to test the functions of the primary serial communications (RS-232C) port. To perform the test, you must insert a special loop-back connector into the RS-232C port so that the computer can check the individual pins of the port. Contact your Customer Care Center if you need a loop back connector (or see Appendix B for the signal/pin assignments if you want to make your own loop-back connector). Note that a different connector is required to test the parallel port.

When you select option 11 from the DEVICE LIST, you see these prompts:

Attach loop-back connector to serial port. Enter Y to start this check when connector is attached, or Enter N to return to the menu.

D-28 Performing System Diagnostics