Epson Apex 20020 - Manual (Page 191)

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 A 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.
Insert the loop-back connector. Then press Y and Enter to
start the check.
First, the computer checks the serial port control lines to see
that they are able to change from high to low and vice versa.
No messages are displayed during this part of the test unless an
error occurs.
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 these messages:
RS232C 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 progress is displayed.
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.
Performing System Diagnostics
C-27