HP-488 Oscillator

[jcooper]

I'm looking to replace the 20MHz crystal on my HP-488-02 development board with a 40MHz crystal. Can you tell me who your supplier is for that part so that I can get one in the same package? Also, do you know of any reason offhand why a 40MHz crystal might not work with the board?

[Benj]

Hello

Which PICmicro device are you looking to drive with the 40MHz crystal? Most of the PICmicro devices will not be unable to run at this speed.

[jcooper]

PIC 18F258

I don't think the chip will have a problem, because its UART baud specs include the possibility of running off a 40MHz oscillator. I was more wondering if anything else on the board (the PPP firmware or something) might object to the frequency increase.

[Benj]

Hello

Yes you are correct these devices do support the 40MHz clock. Thats great not spotted that before. You can also use a lower speed clock and use the onboard PLL to boost the program frequency if you wish. There should not be any issues with using a 40MHz clock onboard our hardware. The PPP chip has its own oscillator so you should not run into any problems.

[jcooper]

Ok, thanks for the info. If you can, would you mind telling me who your manufacturer is for the onboard crystal?

[Benj]

Hello

I normally buy ACT

http://www.rapidonline.com/searchresult ... kw=90-1080

or Truxtal

http://www.rapidonline.com/searchresult ... kw=90-3257

However it looks like these manufacturers do not go as high as you would like.

Remember you can always buy a 10MHz crystal and then enable the onboard 4x PLL to boost this speed up to the 40MHz. This can be done through the expert chip configuration screen.