I am having trouble with a board I have had fabricated. The processor is an NXP LPC1788 Cortex-M3.
I am using a 12 MHz external crystal to clock the processor as recommended in the datasheet.
For some reason I cannot get the crystal to oscillate. I'm unsure if I am checking it correctly on my scope, but I cannot see any consistent oscillation.
Here is the datasheet for the crystal: http://www.txccrystal.com/images/pdf/8z.pdf.
It has a load capacitance of 18 pF, the LPC1788 datasheet recommends external load capacitors of 39 pF with a crystal of load capacitance of 20 pF, so I have tried 39 pF load capacitors with no joy. I have also tried 18 pF load capacitors as recommended by LPC1788 datasheet for crystals with approximately 10 pF load capacitance.
I would really like to at least understand why the crystal is failing to oscillate before I do another run of the board, as it is quite expensive (four-layer board).
Here is an image of the crystal routing.