MC9S12 noise immunity

[Alessandro]

Dear everybody,

in the recent past we have manufactured with success boards targeted to control

motorbikes engines using the MC68HC711E9 microntroller.

Now we have replaced the MC68HC711 part with the MC9S12C32MFA25 part in order to

enhance the features of our boards. With great surprise we are detecting some problems

caused by noise released from an inductor coil used to make the spark.

The PCB layout and the components around the microcontroller are the same as our

previous boards. So we suspect that the MC9S12 part has not the same noise immunity

of the MC68HC11 part.

Do you experience our same problems in your applications ? Are we using a not suitable

microcontroller for our application ? How could Freescale help us to workaround these

noise problems ?

Any advice will be very appreciated.

Best Regards

/Alessandro

[Alban]

Hello Alessandro,

The technology of both products is quite different. Still, similar technology products are used for motorbikes without problems.

First, you could check if the S12C32 is qualified for Automotive use. That would be a problem for your product to sell.

Then, I would advise you to check where the problem is: spikes in the oscillator, noise on inputs...

It is also important to describe the effects as this could help in finding a solution. I mean some problems could be addressed by software whilst other manifestations need hardware work.

Cheers,
Alban.