Epson Y16499100301 - Manual (Page 122)

insert a special loop-back connector into the RS-232C port so
that the computer can check individual pins of the port.
Contact your dealer if you need a 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 0 0
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 these messages:
RS232C echo back check - with various data formats
Current data format: 5 data bits, 1 stop bits,
parity - NONE
Current test data is 0 0
D-18
Performing System Diagnostics