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Guide to Printers and Printing
A nonsupported printer is a device that is not supplied with the
operating system.
Choose one of the following methods to configure and drive a nonsupported
printer:
- Configure the device as a supported printer if the nonsupported printer
uses the same hardware interface (serial or parallel) and closely approximates
the functions of a supported printer.
- Configure your printer as a supported printer if there are no supported
printers similar to yours. Change the virtual printer characteristics
to accommodate your printer.
- Use generic as the printer type and the appropriate interface
type if you are unsure if your printer emulates a supported device. The
operating system supplies two generic devices, other parallel printer
(opp) and other serial printer (osp). Specify one
of these devices by selecting the interface type, such as parallel
rs232, and modify the characteristics according to the specifications in
your printer manual.
- Configure your printer device driver and print queue, but set the print
subsystem to pass all print requests transparently to the printer. With
this configuration the application must correctly assemble the printer data
stream. The print spooling subsystem is available for sharing the
printer among users, but the virtual printer system does not format the
printer data stream.
- If your output device has special formatting requirements, such as an
electrostatic plotter that requires input as raster graphics, substitute the
formatting software for the printer formatter or the printer backend
program.
You must define a virtual printer to support the features of the
nonsupported printer and the print spooling subsystem.
- You must identify the printer data stream that best matches your printer
to customize a nonsupported printer. The operating system supports the
following data streams through predefined virtual printers:
asc
| Extended ASCII
|
pcl
| Hewlett-Packard LaserJet
|
gl
| Plotter
|
ps
| PostScript
|
630
| Diablo 630
|
855
| Texas Instruments 855 dot matrix printer in dp mode
|
- Once you have identified the data stream used by your printer, choose
either a supported printer that uses the same data stream or one of the
generic printers and customize the definition for your printer.
You may need to adapt your
nonsupported printer so that it functions properly with the base operating
system serial printer device driver:
- The following chart
details what the RS-232 signals mean to the serial printer device
driver:
RS-232 Signal
| Serial Printer Device Driver Use
|
FG
| Frame ground. Often used as shield.
|
TxD -->
| Used to transmit data to printer.
|
RxD <--
| Used to Receive data from printer.
|
RTS <--
| Held high after printer port opened. Provides host status to
printer. Not used for data pacing.
|
CTS <--
| Must be high for printer port to be opened. Used to detect that
the printer is turned on.
|
DSR
| Not used. Usually tied to DCD.
|
SG
| Reference voltage for signals.
|
DCD <--
| Used for data pacing when DTR is set to yes.
|
DTR -->
| Held high after printer port opened. Provides host status to
printer.
|
- If you use FG as a cable shield, make sure that it is only connected at
one end. It makes no difference which end is connected. This
provides an efficient shield against electrical noise.
- If your RTS signal is used to supply voltage to CTS on the printer port,
check to see what your printer does with its RTS signal.
Although RTS and CTS data pacing is not supported on serial printers, the
device driver will block the open of the printer port until the voltage of CTS
becomes high. The CTS signal is usually supplied by the RTS signal from
the printer. However, some printers use the RTS signal for data
pacing. These printers drop RTS when they want the system to stop
sending data. Since the queuing system always needs the port opened to
check for status, if the printer drops the RTS signal, the port closes and the
queue goes down.
- Some printers require that you raise the voltage of DCD and DSR or CTS on
the printer side. There are several methods for raising the
voltage:
- Use DTR or RTS on the computer side to supply the voltage.
OR
- Obtain the voltage from the printer side.
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