The HRCAP has some variation in
performance, this results in a probability distribution which is described using
the following terms:
Accuracy: The time
difference between the input signal and the mean of the HRCAP’s
Precision: The width of
the HRCAP’s distribution, this is given as a standard deviation.
Resolution: The minimum
Figure 7-49 HRCAP Accuracy Precision and
Typical core conditions: All
peripheral clocks are enabled.
Noisy core supply: All core
clocks are enabled and disabled with a regular period during the measurement.
Fluctuations in current and
voltage on the 1.2-V rail cause the standard deviation of the HRCAP to rise.
Care should be taken to ensure that the 1.2-V supply is clean, and that noisy
internal events, such as enabling and disabling clock trees, have been minimized
while using the HRCAP.
Figure 7-50 HRCAP Standard Deviation