FAQ: How does the Oscillator Comparator Unit detect a clock fault?

The Oscillator Comparator Unit (OCU) uses an auxiliray clock called the Low Frequency Oscillator (LFO) with a known value and compares cycles counts to the programmed value for the primary Clock signal.

The LFO clock signal is divided by 16 before entering the OCU. The ADSP-CM419 EZ-Kit uses a 16 MHz crystal for the LFO, and is divided by 16, thus 1 MHz in the OCU module block. The OCU uses the LFO to increment a counter during each core clock cycle, and if the counter goes out of range from the programmed setting, then a clock fault is issued.

When programming the OCU, make sure the programmed LFO frequency is the LFO crystal divided by 16.