To read system time, read register 0057h first.
This reads the current system time to a cache and prevents the value from changing when other system time registers are accessed.
After reading the register 0057h, read registers 0058h ... 005Ch to get month, day of
month, hours, minutes, and seconds.
The reading order of these registers is free.
To write the system time, set the year, month, day of month, hours, and minutes by the
means of the registers 0057h ... 005Bh.
This writes the date to the cache.
To finish updating the system time, write seconds to register 005Ch.
This updates the system time immediately by applying all the recent values from the cache.