So must not change a main chip, QFP128 before not, now disassemble and assemble has been very easy.
But after changing the chip, although you can write the program, but I measured the crystal oscillator, or sex is not, XOUT has.We can confirm that the chip is working normally. Why can't we measure the crystal vibration?Circuit is correct, only check whether there is a problem with the oscilloscope.
The 5V1KHz square wave is normal when the probe is self-corrected on the oscilloscope.So what's the problem?Isn't it energy crystal?No way. I've measured them before
I found the X1 gear for the probe. I tried to change the X10 gear, and suddenly I found that there was a starting waveform.Strange, why does XIN not exist at X1 and X10?
From the probe, I found that it was related to the capacitor of the probe from the web page of a famous brand.
The characteristic parameters of oscilloscope probe are:
Corresponding: x200mhz P2200x10X / 1/6 mhz10mo pf300v mo16pf / 95/150 v / 1
Typically inputc is important here, 95pF in 1X. This capacitance affects the initiation of the crystal oscillator. The crystal oscillator has a matching capacitance of 30pF.If you want to measure whether the vibration starts, use a probe with a small capacitance, such as 10X.
Similarly, from the above analysis, from the accuracy, strictly speaking, oscilloscope measured waveform is inaccurate, not the actual value.Of course, for crystal oscillator, whether or not to add capacitance, and how much capacitance, affect the shape of the waveform quality, will not affect the size of the frequency.So the system will work.