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VLPR Mode Not Initializing Correctly

Question asked by Robert Ryan on Sep 16, 2013
Latest reply on Sep 24, 2013 by Robert Ryan

Hi All,

 

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:

 

_lpm_set_clock_configuration(BSP_CLOCK_CONFIGURATION_2MHZ);

_lpm_set_operation_mode (LPM_OPERATION_MODE_WAIT);       

 

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.

 

Rob

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