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µVISION DEBUGGER: Port 1 Error Message Box

Information in this article applies to:

  • Keil PK51 All Versions


I'm running the debugger and I receive the following error message:


You have tried to modify a port pin which is configured as output!

Why am I receiving this message?


This error happens when you try to input some data into Port PIN and, at the same time, you're outputting data.

For example, the instruction

P1 ^= 0x01;               /* Toggle P1.0 each time we print */

During the execution of this instruction, if you manually try to change the state of the physical P1.0 PIN ( Pins ) you will receive this error message. It means that you are outputting and inputting a signal over the port pin at the same time.


You may modify Port Pins when you are not outputting data over it.

Last Reviewed: Tuesday, February 23, 2021

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