µVISION DEBUGGER: Access Breakpoints on Absolute Memory Write

Information in this article applies to:

• µVision Version 2.20 and later

QUESTION

The µVision debugger offers access breakpoints that can halt program execution when an application writes to a specify memory location. It is possible to combine access breakpoints with a value when I have symbolic information from the C compiler. For example, I can define:

BS write myVar == 0x5A

This stops execution when the C program writes the value 0x5A to the variable myVar.

However, I want to stop execution when my assembler program writes 0xE8 to the xdata address X:0x0668. How can I define such a breakpoint?

ANSWER

Since the assembler program does not provide type information, you need to use the built-in functions _RBYTE, _RWORD, _RDWORD, _RFLOAT, and _RDOUBLE to check the value that is stored in memory. You can then set the built-in debugger variable _break_ to halt program execution.

From the command line you may define such a breakpoint is defined as follows:

BS write X:0xE50, 1, "_break_ = (_RBYTE(X:0x668) == 0xEA)"

From the Debug - Breakpoints... dialog you can define this breakpoint with the following inputs:

• Expression: X:0x668
• Count: 1
• Command: _break_ = (_RBYTE(X:0x668) == 0xEA)
• Access: Write, Size=1 Bytes

MORE INFORMATION

• Refer to Breakpoints Window in the µVision User's Guide.
• Refer to Error E065 in the µVision User's Guide.
• Refer to _RBYTE in the µVision User's Guide.

SEE ALSO

• µVision DEBUGGER: Breakpoints in Memory Regions

Last Reviewed: Thursday, February 4, 2021