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MSP432 RAM retention in LPM3 mode

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Hi,

 

I have been trying to run my Pico]OS port (a simple RTOS) on MSP432. Everything is mostly working nicely,

but I got into problems when trying to enter LPM3 mode. After digging into this I suspect

that RAM contents is lost when LPM3 mode is entered, which causes my system to crash.

 

If I add call to 

 

MAP_SysCtl_enableSRAMBankRetention(SYSCTL_SRAM_BANK7)

 

into my startup things seem to work.

 

However, the msp432 user guide SYSCTL documentation says in table 4-13 "SYS_SRAM_BANKRET register description" 

that on reset all BNKx_RET bits should be set to 1, ie. all banks should be kept. I'm wondering if I have understood

something wrong or is the documentation incorrect ?

 

If I look at driverlib "wdt_a_interval_mode" example, there seems to be a call for MAP_SysCtl_enableSRAMBankRetention also,

which suggests that it would really be necessary.

 

Startup code (along with pico]os stuff) is at https://github.com/AriZuu/blink-test/blob/master/msp432/startup.cif someone

is interested.

 

   Ari S.

 


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