12Mhz crystal to MSP430F67651

Apparently, the F67651 only supports low-frequency (32768Hz) crystals.
Experiments with the G2 devices (with a similar limitation) have revealed that in bypass mode, a HF clock signal from an external oscillator with TTL output can be injected (well, not really low-power then, depending on the used oscilaltor). However, this is outside specs and not guaranteed to work with future silicon revisions.
But, there have been no reports yet for successful trying this with a 5x/6x device.

If you try., please come back and tell.