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Netport(R) II Print Server: Parallel and Serial Port / Cable Issues
Contents:
PARALLEL CABLE LENGTH
The maximum supported length of the parallel printer cable is 6 feet.
Using the NetPort(R) II print server with a cable that exceeds 6 feet
may result in printing problems such as; garbage charaters, not printing
at all or intermittent printing.
PARALLEL PORT PIN ASSIGNMENTS
The NetPort(R) II follows the Centronics parallel port standards. The
rule of thumb is that if the printer will work attached to a PC, then it
should work with the NetPort II print server.
i=input to printer
o=output from printer
Pin #Signal
1 i strobe- (low for handshake)
2 i Data bit 0
3 i Data bit 1
4 i Data bit 2
5 i Data bit 3
6 i Data bit 4
7 i Data bit 5
8 i Data bit 6
9 i Data bit 7
10 o ack- (normally high - low when ready for next
character)
11 o busy (normally low, high to hold off handshaking)
12 o papererror (normally low, high for paper problems)
13 o select (normally high, low for off line)
14 i autofeed- (held high)
15 o error- (normally high, low for error)
16 i init- (held high)
17 i selectin (held high)
18-3 Various
At least one ground signal from the printer must be connected to at
least one of the NetPort's pins 18-25 via the parallel cable. The
printer grounds occur somewhere in the range of 18-36. Some
manufacturers put strange functions on these pins. Any pin in the 18-36
range that is not ground should not be connected to the NetPort.
If busy or papererror is high, or select or error is low, NetPort will
not print. The timing of the handshake signals strobe-, ack-, and busy
can cause problems.
NOTES ON THE SERIAL PORT
1. The cable must be a serial printer cable (a modem cable will NOT
work with printers). Some printer manufactures require specific
cable pinouts. Check your printer manual for the recommended
cable. This document has three cable pinouts that may be helpful.
Note: Serial printer cables and modem cables are NOT the same and can
NOT be used interchangeably for printing purposes. A modem cable
connects a DTE (data terminal equipment) device to a DCE (date
communication equipment) device. This requires a cable that connects
TXD to TXD, RXD to RXD etc. Whereas, a serial printer cable connects
TXD to RXD, RXD to TXD, CTS to RTS etc. Refer to the NetPort(R) II
print server manual for detailed pin out examples of serial printer
cables.
The maximum cable length is 50 feet. Using the NetPort II with a
cable that exceeds 50 feet may result in printing problems such as:
garbage characters, not printing at all or intermittent printing.
2. The handshaking parameters must be set the same for the NetPort II
and the printer. By default the NetPort's parameters are set to
9600 baud, NONE parity, 8 databits, 1 stopbit, XON-XOFF handshake.
If the printer is not set to all of the above parameters, either
the NetPort II print server or the printer must be changed. To
change the printer consult your user's manual. To change the
NetPort II, use Netport Manager to reconfigure the port settings.
Select Configure/Hardware/Ports and set the serial port options to
the required settings.
Note: The default parameter will work with the HP Laserjet printer. Rev
003 of the Ethernet manual is incorrect. Also, we have found that the
cable is the frequent cause of serial printing problems.
Note: When using the NetPort II serial port in Print Server mode with HP
Plotter, it is usually preferred to use the XR handshake.
SERIAL CABLE WITH HP PRINTER
The following serial cable has been tested and will work with the HP
Laserjet series printers and plotters:
DB-9(NetPort) DB-25(HP laserJet)
DCD 1--------------------4 RTS
RXD 2--------------------2 TXD
TXD 3--------------------3 RXD
DTR 4--------------------5 CTS & 6 DSR
GRN 5--------------------7 GND
DSR 6 & CTS 8------------20 DTR
RTS 7--------------------8
SERIAL CABLE WITH APPLE LASERWRITER
The following serial cable has been tested and will work with the Apple
laserWriter series printers:
DB-9(NetPort) DB-25(Apple LaserWriter)
RXD 2--------------------2 TXD
TXD 3--------------------3 RXD
GND 5--------------------1 GND & 7 GND
DSR 6 & CTS 8------------20 DTR
RTS 7--------------------5 CTS & 6 DSR
GENERIC SERIAL CABLE
The following serial cable is a generic RS232 serial cable and will work
with many standard printers:
DB-9(NetPort) DB-25(serial printer)
RXD 2--------------------2 TXD
TXD 3--------------------3 RXD
GND 5--------------------7 GND
DSR 6 & CTS 8------------20 DTR
RTS 7 -------------------5 CTS & 6 DSR
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