Xerox 4520 用户手册

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

WUG-APPC Page 2 Black,Cyan Sunday, January 22, 1995 9:07 PM