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Err: Cannot Write to LPTx Printing to Parallel Port

This article was previously published under Q181022
This article has been archived. It is offered "as is" and will no longer be updated.

IMPORTANT: This article contains information about editing the registry.Before you edit the registry, make sure you understand how to restore it ifa problem occurs. For information on how to do this, view the "Restoringthe Registry" online Help topic in Regedit.exe or the "Restoring a RegistryKey" online Help topic in Regedt32.exe.
When you print to a parallel port on a computer running Windows NT, one ofthe following may occur:

  • After you clear a paper outage or jam on the printer and click OK on the following error message, the same error may reappear until Windows NT is shutdown and restarted:

    Cannot write to LPTx

    where x is the LPT port number.
  • On host-based printers, the printer does not reset properly if you shutdown and restart Windows NT without first actually powering off the computer.
  • When you print with an older parallel port printer, the output has invalid, garbled, or missing characters or nothing prints.
The first two symptoms above are caused by the local port monitor resettingfaster than the port can become ready. The printer driver then interpretsthat the printer is properly reset, which is not the case.

The third symptom happens because the centronics handshake inParallel.sys is too aggressive for some older devices.
To do a slower handshake to older/slower printers, the following registryentry must be added.

WARNING: Using Registry Editor incorrectly can cause serious problems thatmay require you to reinstall your operating system. Microsoft cannotguarantee that problems resulting from the incorrect use of Registry Editorcan be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys AndValues" Help topic in Registry Editor (Regedit.exe) or the "Add and DeleteInformation in the Registry" and "Edit Registry Data" Help topics inRegedt32.exe. Note that you should back up the registry before you edit it.If you are running Windows NT, you should also update your Emergency RepairDisk (ERD).

The registry entry to enable this feature is

and is a DWORD value "UsePIWriteLoop", which needs to be set to 1.

Be aware that enabling this entry will slow down ALL parallel ports.

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack

For your convenience, the English version of this post-SP3 hotfix has beenposted to the following Internet location. However, Microsoft recommendsthat you install Windows NT 4.0 Service Pack 4 to correct this problem.

Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.
lpt1 lpt2

Article ID: 181022 - Last Review: 10/07/2013 19:28:06 - Revision: 2.2

Microsoft Windows NT Server 4.0, Terminal Server Edition, Microsoft Windows NT Workstation 4.0 Developer Edition, Microsoft Windows NT Server 4.0 Standard Edition

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