LOGGER and FDX trace are both software trace methods which require a modification of the target application in order to write specific trace information to a reserved buffer on the target memory using a trace format provided by LAUTERBACH. 

For LOGGER trace, TRACE32 loads the trace information, after stopping the recording, from the target memory for display and processing. The trace is limited by the size of the reserved buffer on the target memory.

FDX trace streams the trace information on run-time to the TRACE32 PowerView software on the host via memory access on run-time, or Arm DCC. The buffer reserved on the target is thus used as temporary FIFO. This way longer trace recordings can be achieved. If the used channel  cannot transfer the collected trace information on time, the execution is stalled by the FDX target code to avoid losing trace data (target FIFO overflow). "Stalls" are displayed in the FDX window.

Please refer for more information to

• Application Note for the LOGGER Trace
• Application Note for FDX > chapter "FDX Software Trace"
• LOGGER trace videos
• FDX trace video