Last Branch Record (LBR) trace is selected by default the first time you open the Execution Trace window .
Note that LBR trace does not use a memory buffer.
To enable it, right-click within the Execution Trace window and select Enable trace from the context menu. Alternatively, click the trace icon in the Execution Trace window's tool bar.
When LBR trace is enabled, the last 16 taken branches are decoded automatically every time execution stops. Single-stepping is not recommended when the trace is enabled. Instead, set a breakpoint to the interesting location and let the target run to it.