AnsweredAssumed Answered

Touching the TMS/!BKPT PIN on MCF52259 locks up the entire processor, no watchdog recovery

Question asked by Carl Norman on Dec 7, 2014
Latest reply on Dec 8, 2014 by TomE

Hi All,


I have found a way to completely lock up the MCF52259. Simply touch the (pin 38 TMS/!BKTP) (I used my finger, tweasers, cro probe and they all locked it up completely). It just stops, watch dogs don't recover (I have both watchdogs running and neither reset it), nothing other than pulling reset low manually or power cycling recovers from this. MC_CLK is still running and stable, I have loss of lock etc enabled and nothing happens, all code stops instantly exactly where it just stops where it was with all IO left exactly where it was. This will happen on the MCF52259DEMO / EVAL board. There is a 10K pullup to prevent this strange operation, how can it still happen with such a high impedance touch???? Sure if it was floating, but 10K pullup is small enough...


Why doesnt the watchdog recover from this, is it because its activating the external break point?? I have DSI floating, DSO pulled high. Is the internal bus locking up stopping all code and all modules from getting a clock i.e. watchdog stops ticking?


Any idea how to stop this on boards in the field as I cant add any circuits via remote software update.


Also, are there any other known pins or issues that I should allow for?


PS I have JTAG enable directly tied to ground