The DS1925 Mission Start Delay (MSD) counter differs from the MSD counter found in the DS1922X/DS1923 iButton data loggers. This counter, starting at address 0x0216 through 0x0218, is used to set the amount of time delay desired before a data logging "mission" starts logging data. For the DS1925, these addresses, when read, will not not give a count down of the time left before the mission starts. The registers will only show what was set in them, which is the orignal MSD value. The start delay feature of the DS1925 works -- the delay still happens, but the memory locations will not give the "time left before mission start" like the DS1922X/DS1923 data loggers.
So, DS1925 customers writing custom software and who require to find the "time left before mission start" should save the time that the mission was initialized. The current time read from the iButton data logger minus this saved time gives how much time of the MSD has elapsed. So, mathematically, this would be: MSD - MSD elapsed = "time left before mission start".