hello
1. Remove the AC256 daugther card of your DEMOAC
2. Ensure that the jumpers USB_BG (BGND and RST) are presents
3. Set the "PWR_SEL" jumper on "VR1" and do NOT connect external power source to your DEMOAC, ensure the the switch PWRSW is OFF.
4. Connect your own board with the MCF51AC256 to the 6-pin BDM connector "BDM_PORT"of your DemoAC
The embedded Multilink BDM automaticaly sense (and adapt) the target voltage(3V3 in your case).
thierry