Hello and thanks always.
I am using the PIC18F2550.
In my projects so far I have been using the Internal oscillator for non-USB projects and with for USB projects a board containing a PIC18F2553 (similar to 2550) and a crystal of 20MHz. Now the circuit outside OSC1 and OSC2 is similar to Figure 2-2 of the datasheet.
According to the recommendations of the datasheet with 20Mhz, C1 and C2 should be 15pF. However my board comes with C1 and C2 of 22pF. This does not represent a problem.
Now I am planning of building my own board and I only have a 24Mhz crystal at hand. I have already found the changes of configuration I have to do to reproduce the 20Mhz behavior but my question is
1) What value of capacitors is advisable to use?
2) what for are these capacitors?
The crystal I am planning to use is http://www.digikey.jp/Web Export/Supplier Content/Citizen_300/PDF/Citizen_HC49US.pdf?redirected=1
Now, I found this page:
https://blog.adafruit.com/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/
in which they recommend C1 and C2 in a formula like C1=C2= 2*CL-2*Cstray but how much should I put for CStray??
--------------
Now, my other question is in the Table 2-3 they give a series of oscillator configurations but since USB highsepped can only have 48MHz as clock , does this mean I have to always use PLL or use a crystal of 48MHz to directly drive it through USBDIV?? (see Fig 2-1)
(Just in case, datasheet is here
http://ww1.microchip.com/downloads/en/devicedoc/39632c.pdf
I am using the PIC18F2550.
In my projects so far I have been using the Internal oscillator for non-USB projects and with for USB projects a board containing a PIC18F2553 (similar to 2550) and a crystal of 20MHz. Now the circuit outside OSC1 and OSC2 is similar to Figure 2-2 of the datasheet.
According to the recommendations of the datasheet with 20Mhz, C1 and C2 should be 15pF. However my board comes with C1 and C2 of 22pF. This does not represent a problem.
Now I am planning of building my own board and I only have a 24Mhz crystal at hand. I have already found the changes of configuration I have to do to reproduce the 20Mhz behavior but my question is
1) What value of capacitors is advisable to use?
2) what for are these capacitors?
The crystal I am planning to use is http://www.digikey.jp/Web Export/Supplier Content/Citizen_300/PDF/Citizen_HC49US.pdf?redirected=1
Now, I found this page:
https://blog.adafruit.com/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/
in which they recommend C1 and C2 in a formula like C1=C2= 2*CL-2*Cstray but how much should I put for CStray??
--------------
Now, my other question is in the Table 2-3 they give a series of oscillator configurations but since USB highsepped can only have 48MHz as clock , does this mean I have to always use PLL or use a crystal of 48MHz to directly drive it through USBDIV?? (see Fig 2-1)
(Just in case, datasheet is here
http://ww1.microchip.com/downloads/en/devicedoc/39632c.pdf