Xerox Paris, a document system Support & Software User Guide

Overview of using Serial as the Input Source

When you select ‘Serial’ as the Input Source, you will be required to set up
your serial port settings.

Before setting up your serial communications, it is important to understand
serial communications and the configuration of your PC.

Understanding Serial Communications

It is not within the scope of this manual to enter into a full explanation of serial
communications, however, in order to avoid problems there are some issues
that need to be understood.

Hardware Overrun Error Messages

A common problem with serial communication is ‘hardware overrun’ error
messages. The simple answer to their cause is that the baud rate is too high, but
there are other factors and there are simple solutions.

High Baud Rate

Hardware overrun errors and the frequency of this error depend on the PC
configuration, however the baud rate is normally the most critical factor.
Generally the higher the baud rate, the greater the probability of a hardware
overrun.

UART Signals an Error

The hardware overrun error indicates an overrun error of the receive buffer in
the Universal Asynchronous Receiver Transmitter (UART). The Comm driver
obtains this error by reading the Line Status Register (LSR) of the UART, of
which bit 1 is set when an overrun occurs.

When the Comm driver cannot service a Received Data Available interrupt,
before it receives the next transmitted character, the UART signals an error
because at least one character has been lost.