I need a sample schematic using the MC9S12DT128. My circuit I designed isn't working.

[gerryhermann]

I designed a circuit around the MC9S12DT128BMPV. I'm using an external 16MHz clock. When I power up there are some erratic square wave signals on the I/O pins. It seems like it is going through some type of continuous reset. I have the reset line pulled high with a 5K resistor. CW with a Cyclone can't communicate. Any ideas?

[iggi]

Hi Gerry,

I would like to recommend you an app note, the AN2727 Designing Hardware for the HCS12 D-Family:

cache.freescale.com/files/microcontrollers/doc/app_note/AN2727.pdf

Kindly go through it and check if you have anything different than stated in the app note such as:

- Power supply connections

- Control pin connections

- Oscillator options

etc.

Regards,
iggi