Capacitor Value when using 40 MHz external mode

kkobraa · Joined: 28 Sep 2003 Posts: 9 Location: AR, USA

Hi,

I'm working on PIC18F2220. Does anyone know the values of capacitors when using 40 MHz crytal for external mode. Thanks.

Ken.

MGP · Joined: 11 Sep 2003 Posts: 57

You can't use a 40MHz crystal with the 18F parts. You can only use a 10 MHz crystal and enable the 4x PLL mode or external oscillator if you want to run at 40 MHz.

Check the datasheet for your particular part, but I believe the maximum crystal frequency you can use is 25 MHz.

Also check the errata sheet for your device, several of the newer 18F PICs have problems running at their full rated speed.

LHart · Joined: 22 Apr 2004 Posts: 1 Location: NL

Hi,

You can't use the PIC 18F with a clock of 40 MHz. We use the PIC 18F8720 at a frequency of 22.1180 MHz. The limit wich microchip specifies in the newest datasheet of the 18F8720 is 25 MHz.

The PIC 18F6520 is now available with 64 kbyte flash, and a speed of max 40 MHz.

Microchip is developping a new PIC18F8721 with 40 MHz clock speed and 128 kByte flash memory. You can use ext flash and a PIC18F6520 micro, so you have much memory and a high speed.

Regards,
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LindertVanderHart

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

The fastest operating is achieved with a 10Mhz xtl and the fuse set to 4xPLL.