The datasheet says:
If BOD is disabled by software, the BOD function is turned off immediately after entering the
sleep mode. Upon wake-up from sleep, BOD is automatically enabled again. This ensures safe
operation in case the VCC level has dropped during the sleep period.
Does this mean that it does know if the voltage dropped below the BOD during the power down?
No.
Since the CPU is sleeping, a low voltage can not cause the cpu to malfunction, but by reenabling BOD upon wakeup, if voltage is too low for safe cpu operation, the cpu will be held in reset waiting for proper operating voltage.
Jim
If it goes low enough though (while in power down say), can the contents of memory become corrupted? I've always thought of the BOD has being an element that ensures the integrity of the processor state/memory.
can the contents of memory become corrupted?
Assuming by memory you mean RAM, if the voltage drops below the POR level, regardless if cpu is sleeping or not, a reset will happen, and RAM contents does not matter, as it should be initialized upon startup to known values.
If voltage stays above POR level while sleeping, RAM contents will be preserved.
Jim
Can the power on reset be thought of as a lower voltage BOD that is always enabled?
That's one way to look at it, Yes.
Thanks Jim!!!
