next-generation (now) MPU discussion / Backup battery on PMU only

Andy Green andy at openmoko.com
Thu Apr 24 12:48:54 CEST 2008


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Somebody in the thread at some point said:
| Andy Green wrote:
|> Well fine, but what does giving the MSP430 the battery backup actually
|> get us?
|
| Allow us to get out of PMU.Standby, maintain GPIOs while in PMU.Standby,
| etc.

I think there is a bit of confusion here.  "Standby" is a separate issue
that does not need battery backup on MSP430.  IO_3V3 rail is up during
standby.  MSP430 will be up during standby.

The ONLY scenario we consider is no external power, and battery is
removed.  Why do we need MSP430 state to survive it?   I don't think we
need this since we only want RTC to stay up and the RTC can be in PMU.

If it is true we need to keep RTC in PCF50633 and keep the battery on
there only.

- -Andy


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