Why, when PA (and PC0~PC3 for HT82K68A/HT82K68E) is low the device cannot wake up?
Answer The PA port (and PC0~PC3 for HT82K68A/HT82K68E) pins can all be configured to wake up the device but are activated only on a low going edge. If the corresponding PA pin was low when the HALT instruction was executed then the low logic state of this pin will have no wake up effect as no low going transition exists.