Service manual

Running the Dell Diagnostics: Dell Latitude CP
Although the following symptoms can be caused by faulty peripherals or software errors, these
symptoms might also suggest a port problem:
● If a peripheral works intermittently or produces intermittent errors, the port may be faulty.
● If the computer displays an error message that is related to the external device
connected to a port, but corrections to the device do not resolve the error, run the
appropriate subtest in the Serial/Infrared Ports test group.
Subtests
The four subtests in the Serial/Infrared Ports test group confirm the following port functions:
● Serial/Infrared Baud Rate Test
Checks the baud rate generator in each serial communications chip against the
computer's clock
● Serial/Infrared Interrupt Test
Checks the serial port's ability to send IRQs to the microprocessor
● Serial/Infrared Internal Transmission Test
Checks several internal functions of the serial port using the internal loopback mode of
the serial communications chip
● Serial External Transmission Test
If a loopback device is attached, checks the line control bits of the serial port and sends
a test pattern at several baud rates, checking the returned values
Parallel Ports Test Group
The subtests in the Parallel Ports test group check the computer's interface with external
devices, such as a printer, that are connected to the computer through the parallel port. The
subtests in this test group are not intended as a diagnostic test for the actual peripheral
attached to each port.
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