I am working on implementing a power savings schema on our latest design (K60 based) and I have run into an odd behavior. I am using the low power module in MQX 4.0 to accomplish the switching into the various power states.
My entry into VLPR is as follows:
Nothing too exciting. As expected, the overall current on my boards drops from 88 mA to 3 mA, but the UART does not function as expected. After some chasing I have located the code where the code is hanging, but I have no idea why. If I comment out the code (a hack for testing only), everything works great. Power goes to where I expect and the UART behaves as expected. The suspect code is:
while (0 == (PMC_REGSC & PMC_REGSC_ACKISO_MASK))
This code is in _lpm_set_cpu_operation_mode.
Obviously I am missing a setup step, I am just not sure what exactly it is!
Any help would be appreciated.