MCF5223x ESD problems and hang up

[RValls]

Hi everyone!

We are having problems with ESD which cause the MCF52233 in our devices to halt.

The symptoms are that, without the debugger, the device just stop working, it hangs. With the debugger attached, it shows in CodeWarrior as the uC has halted at some random instruction.

At first, we though it was a software problem, just because some error condition in any bus (I2C, SPI) wasn't handled and it hanged up in an endless loop. We have refactored our code and solved all this issues.

After that, the problem remained, and then we have sought for hardware problems.

We have changed the behaviour of the BKPT pin in order to cause an interrupt instead of halt the device, by writing to the debug CSR register.

We have tried to disable the BDM mode by pulling up the JTAGEN pin.

We have checked that the TEST pin is correctly connected to GND (and even connected it directly to the GND of the source).

None of this has solved our problem.

Are we missing something that still causes the uC to halt?

Best regards and thanks in advance,

Ruben

[TomE]

The chip has internal RAM and FLASH so it should be more immune to ESD than one with external memory.

Are you failing a "standard ESD certification test" or is it failing in the field?

What is an acceptable outcome? Does it have to keep running or is it OK if it resets and recovers?

If the latter, have you tried programming the Watchdog? That might work, but sometimes the ESD event is severe enough to stop the watchdog from working. You may need an external hardware watchdog in your design.

Can you isolate the part of the circuit that is sensitive? Start disconnecting things. Start shielding things. Start adding capacitors and zeners and transorbs. Is the power supply OK? It might be dropping out. The Crystal may be glitching or stopping.

Tom