I have built a small board according to the phillips appnote such that I can use the FlashMagic ISP software to reprogram in circuit. I use the three reset pulse method to place the device in ISP mode.
so wh
My device will use an external crystal (11.059Mhz) on board.

My question is, once the configuration bytes are changed such that the chip is told to use an external xtal. If I were to take the xtal off the circuit, could it be reprogrammed using flash magic? Or would the xtal need to be present?

I'm sure your saying, why would you do that?!?! But sometimes we need to take the PLCC chip out of circuit and directly attach it to our ISP board without a XTAL.

Thanks
Mika