Xerox 4520 - Manual (Page 266)

C-2 ❖ 4 5 2 0 / 4 5 2 0 m p U s e r ’ s G u i d e
The 4520/4520mp printers provide a parallel port, serial port,
and three additional network interface port options, all of
which may be active at the same time . Automatic switching
among all active I/O (input/output) ports is supported.
Port Polling Without a Hard Disk Installed
To coordinate automatic switching among the ports, the
printer monitors the parallel, serial, and network interface
ports for incoming data. When a print job is detected on one
port, the printer sends a busy signal to the other ports and
queues the print job into memory for processing. This is
called port polling . Note that while all ports may be
simultaneously active, only one port at a time is able to
receive a print job.
When print jobs are pending on all five ports (parallel, serial,
Ethernet, LocalTalk, and Token Ring), the port polling
sequence is:
1 Parallel
2 Serial
3 Ethernet
4 Token Ring
5 Back to Parallel
LocalTalk is not a part of this sequence. When a print job is
detected on the LocalTalk port, the print job is put in the
queue immediately after any current job finishes.
Note
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