3.3.8. Auto-calibrate timings and using a TPIU pattern generator

Check the Auto-Calibrate Timings option to enable the ARM Profiler to work on targets whose trace signals have imperfect timing characteristics. The auto-calibration runs instead of a standard profiling run, but you need only use this option once per target configuration feature because it writes suitable timing adjustments into the configuration file. Subsequent ARM Profiler-enabled runs use these adjustments to capture uncorrupted trace packets from the target, using trace output from the target to determine when the data signals transition in relation to the clock edge. Trace packets, or other patterns, must be output on the trace signals to accomplish this. By default, the ARM Profiler achieves this by running your image with streaming trace enabled.

The Use TPIU Pattern Generator (TPIU) option activates the other method of generating output on the trace lines. This is only available on targets that have a TPIU and support test pattern generation. Checking the Use TPIU Pattern Generator option tells the ARM Profiler to:

  1. check that the target has a suitable pattern generation facility

  2. make use of it if it does.

Disable this option if you suspect that your target's TPIU is not generating patterns correctly and wish to use trace generated by the image. In most cases, it is preferable to use the pattern generator if one is available on your target, as it produces reliable transitions on all of the trace data signals, while your applications may not.

Note

The ARM Profiler disables the Use TPIU Pattern Generator checkbox unless you have checked the Auto-Calibrate Timings checkbox.

During execution, the ARM Profiler samples signals for data transitions until one of the following conditions are met:

Note

You must provide an executable to run Auto-Calibrate. If you choose to run the Dhrystone example, set the iteration count to one billion. This gives the ARM Profiler enough time to complete the auto-calibration of your hardware.

After a successful auto-calibration, reset your target.

Note

You should run another auto-calibrated session if you increase the port size option within the ARM Profiler because you will be using trace signals that are not calibrated.

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