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Information in this article applies to:

  • C51 Version 6.00 Beta
  • C51 Version 6.00


When I try to configure the monitor settings for the µVision Version 2 debugger, I receive the following message:

Error: Can't load driver 'c:\keil\c51\monitor\mon51.dll'

Then, when I start the µVision debugger, I receive the following error messages.

*** Error: 'c:\keil\c51\bin\tp51.dll' not found
*** Error: 'c:\keil\c51\monitor\mon51.dll' not found

What's going on?


The µVision Version 2 debugger is currently not fully completed. It lacks support for the Monitor-51 and several devices. We are working diligently to add support for the monitor and for many more devices. When they are completed, they will be made available on the web at


As intermediate solution you should use the dScope-51 debugger that is available in the C51 Version 5 package. You may invoke dScope-51 via the µVision2 tools menu.

The following steps show how to add dScope51 to the Tools menu in µVision.

  1. From the Tools menu select the Customize Tool Menu item. The Customize Tools Menu dialog appears.
  2. Add a new menu item and enter the following information:
    • Menu Content: Run dScope-51 with @P
    • Command: C:\C51\BIN\DSW51.EXE (the path depends on your installation)
    • Initial Folder: <empty>
    • Arguments: -i @P.INI

Now, you may start the dScope-51 debugger directly from the µVision Tools menu. µVision passes an INI file (having the same name as your project) to dScope.

You may create the INI file using the µVision editor. For example:

---- Example:  HELLO.INI (dScope INI file for HELLO project)
LOAD 8051.DLL      // the device you want to simulate with dScope-51.
LOAD HELLO         // the application you want to load
g, main            // run program til entry 'main'


Additional information is included in the RELEASE.TXT file included with UV2 and C51 V6.00.


Last Reviewed: Saturday, July 9, 2005

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