Content originally posted in LPCWare by Chucky on Sun Oct 31 08:05:16 MST 2010
The LPC13xx's BODCTRL register lets you enable the BOD reset (BODRSTENA), which comes in handy when you need a system which reliably boots even under sub-optimal power conditions (I still remember my still unsolved brown-out troubles with the LPC2103).
Bits 0 and 1 of the BODCTRL register select the BOD reset level. However in the LPC13xx user manual, only bit setting 0.0 is documented as BOD level 1.49 V and bit settings 0.1-1.1 are reserved.
Now this is funny: first they give you register bits for selection, and then nothing can be selected as only one setting is allowed and all other settings are 'reserved'.
However as I needed to increase the BOD voltage, I just tried what happens with setting 0.1 (a reserved setting) eh voila, the BOD voltage is now around 2 Volts and now I can reduce the flash waitstates without the chip to hang on brown-out or slow power-on.
I also tried out the other reserved settings: 1.0 will reset at 2.4 Volts and 1.1 will reset at 2.6 Volts.
So while this seems to work reliably, why is it not documented in the user's manual ?
Has it just been forgotten or is there a problem with the reserved settings ?
Thanks for input,
Chucky :)
