The second test is an echo back check during which the port sends data to itself in a fixed data format, at all the possible baud rates. When this test begins, you see this message:

RS-232C echo back check - at various baud rates

Current baud rate is 75 Current test data is 00

Each baud rate is tested in turn, and the display informs you of the progress of the test. If the port does not become ready correctly, a timeout error occurs. If any data received does not match the data sent, a verify error occurs, and the computer reports the transmitted and received data at the time of the error.

The final test is an echo back check during which the port sends data to itself at 9600 baud, using various data formats. At the start of the test, you see this message:

RS-232C echo back check - with various data formats

Current data format: 5 data bits, 1 stop bits, parity - NONE

Current test data is 00

Once again, if any data received does not match the data sent, a verify error occurs, and the computer reports the transmitted and received data at the time of the error.

Alternate Serial Port Check

Use this option to test the functions of an additional serial communications (RS-232C) port. To perform the test, you must insert a special loop-back connector into the alternate serial port so that the computer can check the port’s individual pins.

This test is identical to the check for the primary serial port. For more details, see the preceding section.

Performing System Diagnostics

D-23