Bambang Priyanto

Problem on switching FEI or FEE mode into FBE mode

Discussion created by Bambang Priyanto on Sep 21, 2006
I'm working on the project that uses battery-operated PCB deploying freescale MC9S08GT60.
To save power in the normal mode, the PCB uses 32K external crystal oscillator in the FBE
(FLL Bypassed External) mode.  However, during power on or reset, I use internal oscillator
in the FEI (FLL Engaged Internal) at 5.5MHz. The problem is that I still cannot switch the mode
from FEI to FBE in low frequency. It always ended up with 4.4 MHz clock.
Another approach, during power on or reset, I use FEE (FLL Engaged External) at 4.5 MHz
using external oscillator. It can switch to FBE at 48KHz, but it does not work reliably during
reset operation. Many times I have to hit the reset switch several times,or it does not work at all.
Can anybody  have good advice or solution? I would appreciate if I can get the sample code.