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Guide to Printers and Printing
Configuring Nonsupported Printers
A nonsupported printer is a device that is not
supplied with the operating system.
Configuration Options
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.
Customizing Nonsupported Virtual Printers
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.
Wiring Nonsupported Printers
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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