They suffer from noise, glitches and ground bounce on-die due to the lack of on-die Vcc decoupling and, especially tragical, suffer from manufacturing tolerances of "Vbad"-thresholds. Also, they seldom work down to Vcc=0V. These thingys often are crap, even if the manufacurer is Silabs or whosoever: What helps a brown-out detector, which can only reset the micro, when first a SFR has to be written to "1"?? Datasheet make believe that these solutions will work, but in reality they fail just too often.

Its perfect, that the MAX1232 contains a watchdog, which needs to be fed. A full off-chip solution!

Kai