Epson Equity 320SX PLUS - Manual (Page 183)

You may see the following message if you attempt to run the
Change line test on a drive that does not support a change
line, such as a 360KB or 720KB drive:
Change line not available
The controller displays one of these messages when an error
occurs during a diagnostics procedure:
Bad address mark
Bad CRC error
Bad DMA error
Bad seek error
Diskette write protected
Media change error
Record not found
Timeout error
These errors could occur because of a faulty drive, controller,
or cable, or if you attempt to run a test on a write-protected
or unformatted diskette.
Miscellaneous Diagnostics
These tests are listed in the Miscellaneous diagnostics
submenu to provide a complete check of the parallel and
serial ports:
Printer adapter test
Comm. adapter test
Printer Adapter Test
This test checks the parallel port and the printer by sending a
pattern to the printer. If the printer does not print the
pattern, the test has failed.
Performing System Diagnostics B-23