µVISION DEBUGGER: Sample buffer size of Logic Analyzer in MDK µVISION

Information in this knowledgebase article applies to:

• MDK v5.x

QUESTION

I have added a few global variables to Logic Analyzer debug window in µVision debug session. After running my program on the target device for a few minutes, the signals captured at the beginning of the execution are truncated and missing in Logic Analyzer window, as shown in the following figure. What has caused this issue?

ANSWER

The recording data buffer used by Logic Analyzer is implemented as a ring buffer and has limited size. The total number of data samples that can be stored and shown in Logic Analyzer is 256k, no matter how many signals/variables are defined in Logic Analyzer. And Logic Analyzer supports maximum up to 4 signals/variables. As soon as all 256k data samples are captured and shown in Logic Analyzer, the old data samples stored in the recording data buffer will be deleted.

For instance, if there is only one signal/variable defined in Logic Analyzer, and the data sample rate of this signal is 1 sample/ms, after 256 seconds all recording data buffer will be filled out. The data samples captured at the beginning of execution will be truncated and lost.

More signals/variables and higher sample data rate for each signal/variable would make the recording data buffer faster get full.

MORE INFORMATION

• Refer to Logic Analyzer in the µVision User's Guide.
• Refer to Restrictions in the µVision User's Guide.

Last Reviewed: Tuesday, August 27, 2019