109
PORT SWITCHING
PROGRAMMING CONSIDERATIONS
Automatic Port Switching
The FormsMaster 8000 series printers will automatically accept data from the Parallel Interface, the
RS-232 Serial Interface, and any optionally installed hardware interface (Coax/Twinax, IPDS Coax,
IPDS Twinax, or 10BaseT LAN). This feature is always active and does not require user intervention
to change ports.
In most installations, the printer is only connected to one computer and this feature may be ignored. In
other installations the printer may be attached to two or three computers. This section describes how
the printer will automatically switch control of the printer from one hardware interface port to another.
Note that since any one of these ports can become active at any time, items which pertain to each port
need to be set up as described in the
FormsMaster 8000 Series Operator’s Manual
. Ports that will not
be used (not installed or not connected to a computer) do not need to be set up. Optional interfaces
that are not installed are not displayed in the Setup menus.
When the first data are received at any port after turning on power to the printer, that port becomes the
“active” port. While one of the ports is active, each of the other ports will accept only a limited
number of characters before reflecting a “busy” condition to the computer attached to those ports.
To change which port is active, the printer’s buffer must be empty for at least 15 seconds and data
must be received from a different port. Therefore, if data are never received from more than one port,
that port is always the active port.
Programming Considerations
It is the programmer’s responsibility to ensure that the port transitions are achieved in a manner that
does not affect their own output or the output from other hosts. This is really no different than running
multible programs on the same host with one major exception.
On a single computer, output is generally spooled or one program has to wait until another program
has finished with the printer. When multiple host computers are involved, this introduces the ability
for one computer/program to interrupt another conputer/program. The printer provides some control of
this interruption by requiring the 15 second delay as described above. Programs that may pause for 15
or more seconds before completion should save their output in a file and then copy the data to the
printer to protect their output from being interrupted by another host.
To help ensure a “clean” transition when the active port changes, the printer will automatically perform
a Carriage Return (CR) and reselect the emulation that was in effect for that port. The default emlation
is set in the Interface Setup Menus for the Serial, Parallel, and EtherLink interfaces. The Coax/Twinax
and IPDS interfaces default to Printek Emulation.. The printer will also perform a Form Feed (FF) if
Summary of Contents for FormsMaster 8000
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Page 89: ...DEC LA120 Emulation 83 VT Vertical Tab VTS Set Vertical Tab Stop...
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Page 140: ...ASCII Character Tables 134 Epson FX Fast Draft Epson FX Draft Epson FX Letter Quality...
Page 141: ...ASCII Character Tables 135 PC Fast Draft PC Draft PC Letter Quality...
Page 142: ...ASCII Character Tables 136 EBCDIC Fast Draft EBCDIC Draft EBCDIC Letter Quality...
Page 144: ...ASCII Character Tables 138 OCR A OCR B...
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