Ross Myers

MCF51JM , XTAL Oscillator not running

Discussion created by Ross Myers on Jun 11, 2009
Latest reply on Mar 13, 2012 by TomE

Hi All,


I'd been working with a prototype PCB using a MCF51JM, everything was progressing fine, then it just seemed to stop working, BDM cannot connect.

This is what I've found.

There is no oscillation on the XTAL/EXTAL pins (It's has an 8MHz crystal).

Reset line is pulsing every 40uS.


So far I've swapped in a new CPU, swapped 5V regs (it has a reset line) and the crystal, but this thing refuses to work now. Before it just quit it had been working ok and I was exectuing code on the MCU, so I know my circuit design is ok to at least make the thing functional.


So what might stop this CPU from running?