Hello,
The i.MX 8M Plus processor has two external input system clocks: a low frequency (RTC_XTALI) and a high frequency (XTALI).
The i.MX 8M Plus datasheet, in Section 3.1.6 states:
Regarding the 32.768kHz external clock , the datasheet recommends: RTC_XTALO is connected to NVCC_SNVS_1P8 (1.8 V) through a 100 Kohm resistor. And the level range of the crystal's ViH is 0.7 x NVCC_SNVS_1P8 to NVCC_SNVS_1P8 , the level range of the crystal's ViL is 0 to 0.3 x NVCC_SNVS_1P8.
Regarding the 24MHz external clock , the datasheet recommends: XTALO_24M is connected to VDD_24M_XTAL_1P8 through a 400 ohm resistor. And the level range of the crystal's ViH is0.7 x Vdd to Vdd + 0.3 , the level range of the crystal's ViL is -0.3 to 0.3 x Vdd.
However, in the schematic diagram of 8MPLUSLPD4-CPU Sheet 8 of 12, (Document No.: SCH-46368, PDF: SPF-46368), the above two resistors are not designed.
Questions:
1) Are these two resistors necessary for the development of the i.MX 8M Plus processor product (due to differences in datasheet and schematic)?
2) Must the ViH and ViL of the crystal oscillator strictly adhere to the specified voltage ranges? If the high-level voltage does not meet the requirements, will the processor still function properly?
Regards,
Canon Medical
Zhipeng Fan
