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Troubleshooting Peripheral I/O Ports ]
I cannot get my printer or other parallel port devices to work properly on my system
Explanation: You are having problems getting your printer to work on the PC.
Generally this manifests itself as the printer not being seen by the computer.
Diagnosis: There are several common causes of this problem. First is physical
misconfiguration, such as loose or incorrectly connected cables. This is usually seen when
the PC is first put together. Problems sometimes result from incorrect printer drivers or
incorrect settings. Also, the use of advanced printer port modes can sometimes cause
- First of all, make sure that you are testing with a printer that you know works. Also,
to test basic connectivity, don't do fancy things like printing color graphics from
Windows. Try printing a plain text file for starters. Test the printer on another PC to
make sure that it is working correctly.
- Check the BIOS setting
that controls the IRQ assigned to the parallel port. Normally, IRQ 7 is assigned to LPT1,
the printer port present on most systems. If you have it set to IRQ 5, then you may have a
conflict with your sound card, since they usually try to use IRQ 5 for themselves.
- If you have ECP mode
enabled on your parallel port, watch out for resource conflicts and also
incompatibilities of various sorts. I have seen devices just not work properly when ECP
mode is turned on, because some software and hardware just does not deal with it properly.
Disable it at least until you resolve your difficulties. Also, ECP mode usually requires
the use of a DMA channel. Sometimes the default DMA channel chosen is DMA 1, which is also
the default for many sound cards. Try changing it to 3 if you are going to use ECP.
- If your printer requires bidirectional communication in order for its driver software to
work properly, you will need to make sure the parallel port is set to enable bidirectional mode.
This usually means setting the port to bidirectional or EPP mode.
- If you are using multiple parallel ports (i.e., LPT2 or LPT3 instead of the more common
LPT1) then you need to double-check to ensure that they are set to correct resources that
will not conflict with other devices.
- Check the driver that is being used to access the printer. Make sure that it is the
correct type and is installed correctly. Try getting an upgraded driver from the
manufacturer's web site.
- Check the external connections to make sure they are not loose. Check the cables running
from the port to the motherboard headers to make sure they are tight as well.
- If you just installed a new system, or especially if you just upgraded your motherboard
in an existing system, and you are using an AT or baby AT style motherboard, you should
have used the cables that came with the board to connect to the parallel port connector on
the back of the system case. These cables are not universal. If you upgrade your
motherboard and try to save time by leaving the old cables in place and connecting them to
the LPT1 port header on the motherboard, your port may not work.
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