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• Receive XON/XOFF - This option is particularly important for a display with
printer, because the device may send XON/XOFF to pace printer data, even
though it may not normally use pacing characters when receiving display data.
This is particularly true if the line speed between the display and the printer is
slower than that between the 3708 and the display, causing the display to buffer
the printer data internally.
• Device Class - This option is set to 4 to define a display with printer.
• Operating Mode - This option is set to 1 or 2 because the port must be
operating in protocol conversion mode for the printer to be used.
• Source Device List for the Printer Authorization Matrix - If the local copy
function is to be used to copy the display screen image to the printer, then the
display's port number must be included in this source device list. To prevent
other users from performing local copy to the printer attached to a display, the
other port numbers should be excluded from this list.
• Interface Type - Either an EIA 232C or EIA 422A can be used between the
3708 and the device. The connection between the printer and the display is not
related to the 3708 and device interface. The primary consideration here is that
the correct type of cable be used.
Other configuration options should be set as appropriate, using the normal
considerations.
LU Session Restrictions
No printer session with the host or local copy from other users is allowed until the
display is operating in an LU type 2 protocol conversion session (either to a host, or
as the 3708 control terminal). After the LU type 2 BIND is processed for the
display, a notification is sent to the appropriate host that the printer is available.
Whenever the display session ends, because of logoff or power off, the printer session
is also terminated, and the printer becomes unavailable for either host data or local
copy data.
Care should be taken when providing display with printer access for switched ports.
Special consideration may be required in the host applications to prevent data that is
intended for one user from being sent to another. This possibility could occur under
the conditions in the following example:
User X dials in to port 7 and requests the host to send print data on the active
session to the user's attached printer.
Before the print completes, or perhaps even before it begins, the connection to
the device is lost. The connection could be lost because of a bad telephone
connection or because someone accidentally powered off the modem on either
end.
The 3708 notifies the host that both display and printer sessions have been lost.
User Y now dials in and makes a connection with port 7 of the 3708 and begins
a protocol conversion session.
The 3708 notifies the host that the printer is now available, and the host begins
sending printer data to user Y that was intended for user X.
Chapter 4. Protocol Conversion Mode
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