The memory contents of the DS1925 are readable after the battery is depleted due to the nature of the non-volatile memory. The power to read the memory does not come through the parasite-powered circuitry of the 1-Wire front end but through the strong pullup delivering power from the PC adapter. The XPC 1-Wire commands are new for this particular device to handle strong pullup reading/writing the memory of the DS1925. This is why the device's memory can be read after the battery is depleted.
