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2396034_en-US
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Part: MPC5746C (Power Architecture Z4, SDK: NXP MPC57xx platform SDK).
In the manual of MPC5746C, it is stated that FXOSC provides 8 -40 MHz output frequency. Please help me in finding the output frequency provided by FXOSC for the following configurations?
1. FXOSC_CTL: OSCBYP = 0 and OSCM = LCP
2. FXOSC_CTL: OSCBYP = 0 and OSCM = FSP
3. FXOSC_CTL: OSCBYP = 1 and OSCM = LCP
4. FXOSC_CTL: OSCBYP = 1 and OSCM = FSP
Please consider default values for the other register fields. Thanks.
Thanks for your response @petervlna.
How can we find the frequency provided by the crystal/resonator(OSCBYP = 0) and external clock(OSCBYP = 1)?
Hello,
The FXOSC module does not generate a specific frequency based on the OSCBYP and OSCM settings. The FXOSC output frequency is always equal to the frequency of the external source connected to FXOSC (crystal/resonator when OSCBYP=0, or external clock when OSCBYP=1), within the supported range of 8–40 MHz.
Therefore, for all four configurations listed, the FXOSC output frequency is simply the external input frequency. The OSCM setting (LCP/FSP) affects the oscillator operating mode, but does not change the clock frequency.
Best regards,
Peter
@petervlna please provide your support for my FXOSC query mentioned above.
How can we find the frequency provided by the crystal/resonator(OSCBYP = 0) and external clock(OSCBYP = 1)?
Please let me know on the above question @petervlna. I want to use FXOSC as clock source for a timer. Based on the frequency it provides i can load a count value into the timer register
Hello,
The MPC5746C does not provide a way to measure or determine the FXOSC frequency from the FXOSC registers. The frequency must be known from the hardware design:
- OSCBYP = 0: FXOSC frequency equals the frequency of the external crystal/resonator fitted on the board.
- OSCBYP = 1: FXOSC frequency equals the frequency of the external clock signal applied to the FXOSC input pin.
To use FXOSC as a timer clock source, the application must use the frequency specified in the board schematic or clock design (for example, 8 MHz, 16 MHz, 40 MHz, etc.) when calculating the timer count value. The OSCBYP and OSCM settings do not affect the frequency itself.
Best regards,
Peter