1 ACCEPTED SOLUTION
Accepted Solutions
@Scarlet wrote:Okay, I will research the differences between the two.
Unfortunately, the link in that AVRFreaks post that I referenced seems to be broken.
But here is a description of what's inside a Crystal Oscillator:
https://www.avrfreaks.net/s/topic/a5C3l000000UcE1EAK/t160729
As you can see, an oscillator is a complete active electronic circuit:
It contains a crystal plus all the active circuitry necessary to make it oscillate and give a nice, clean digital clock signal as output.
The crystal itself is just a passive component:
it requires extra active electronic circuitry to make it oscillate.
In the case of a microcontroller, the oscillator circuitry is usually inside the microcontroller chip (eg, the HSE within the STM32) - so you just need to provide the crystal externally.
Update:
From an article from SiTime describing the difference between a crystal oscillator (XO) and just a crystal (XTAL):
#CrystalVsOscillator #OscillatorVsCrystal
@Scarlet wrote:
- According to the datasheet, HSE_OSC is specified to provide 8MHz, ?
That'll be when it's used as an oscillator - with an external crystal.
@Scarlet wrote:
- However, on the NUCLEO-F429ZI development board, the JFVNY 25.000 oscillator supplies 25MHz?
There you're using an external oscillator, and just feeding a clock signal into the chip - bypassing the chip's own HSE oscillator.
EDIT:
The datasheet actually says that the HSE Oscillator can do 4-26 MHz:
With an external oscillator - ie, bypassing HSE - the clock input can be 1-50 MHz:
Hello,
- According to the datasheet, HSE_OSC is specified to provide 8MHz,
Could you please indicate the page or a screenshot of the page? 8MHz could be generated by the STLink MCO and used in BYPASS mode from your target MCU.
As stated by @Andrew Neil the datasheet indicates that HSE could be in the range of 4-26MHz.
- However, on the NUCLEO-F429ZI development board, the JFVNY 25.000 oscillator supplies 25MHz. I have verified that the SPI clock indeed derives from multiplying and dividing an 8MHz source, but when I measure the JFVNY 25.000 oscillator on the development board, it does indeed supply 25MHz.
According to the schematics there is no even the crystal PCB footprint on the board of the HSE. Could you please tell us which from which reference you did conclude this information. Could it be X3 (the crystal used for the ethernet PHY?
Referring to the Clock tree and considering, if not using the RTC section, is it possible to omit providing the external LSE_OSE?
Yes and you can use PC14(OSC32_IN) and PC15(OSC32_OUT) as GPIOs if you remove R37 and R38.
Edit: "no even the crystal PCB footprint on the board of the HSE" Yes it does but no restriction to populate it with 25MHz crystal.
@Scarlet wrote:In the UM1974 User Manual, it states that "JFVNY 25.000" is the X4 oscillator.
Does it?
I don't see "JFVNY" mentioned anywhere in that document:
I also don't see "X4" anywhere.
That's Rev 10 (Aug 2023) - What revisions of board & manual do you have?
@Scarlet wrote:Although it doesn't specify what part of the oscillation it provides, the document indicates that X3 is the HSE oscillator.
It tells you that X3 is (or would be - it's not fitted) the crystal for the HSE oscillator:
Could you please indicate the page or a screenshot of the page?
I found the "Input Freq HSE 8MHz" setting in the CubeIDE Clock Config. I don't have the development environment at hand currently, but I'll provide a screenshot of the source later.
8MHz could be generated by the STLink MCO and used in BYPASS mode from your target MCU.
So I can use STLink to program the microcontroller without providing an external oscillator externally?
However, the MCU requires an HSE of 8MHz for execution. Right?
According to the schematics there is no even the crystal PCB footprint on the board of the HSE. Could you please tell us which from which reference you did conclude this information. Could it be X3 (the crystal used for the ethernet PHY?
Yes, I mistook X4 for the HSE OSC. I found in the UM1974 User Manual that X3 is the HSE OSC. However, I'm still unclear about the meaning of 'not provided'.
