We have built a custom board that has a MK61FN1M0CAA12 chip. We want to use the OSC0 external crystal as the reference for the system clocks, but we cannot get the chip to activate the crystal, and by activate I mean put a DC voltage on the XTAL0 pin. Without the DC voltage the crystal does not, of course, oscillate. I have rechecked the layout and actual hardware and everything looks correct as far as I can tell.
We have done the following:
1) Verify that PORTA_PCR18 and PORTA_PCR19 (the pins that XTAL0 and EXTAL0 use) are 0.
2) Write 0xA2 to OSC_CR (enable the oscillator, introduce an 8 pF load).
3) Write 0x1C to MCG_C2 (crystal, high-gain, high frequency range)
4) Write 0xA0 to MCG_C1 (selects external reference as system clock source, sets FRDIV such that clock is in right range, enables oscillator)
I am doing all of these things from CodeWarrior using the Multilink Universal debugger. I assume that the chip's clocking state machine can transition in this scenario.
The one clear mistake that we have made is to pick a 20 MHz crystal oscillator, which can't be divided down to 32 kHz. We will replace it with a 16 MHz crystal, or some other appropriate frequency. But seeing as how the crystal isn't even oscillating yet, I don't think that that is the problem at this point.
Any help would be greatly appreciated.
EDIT: I forgot to mention that the MCG_S[OSCINIT0] value never goes to 1, which is expected since the crystal never oscillates.
Message was edited by: Jim Clay