Thanks to all.
My application has about 12 diff slaves seperated along the machine, each having its own rtc (presently DS1643) for event logging purpose.

One master, where i use DS1644 synchronises all with itself once a day. I intend to replace these costly chips. The trial slaves drift with in a day. Trimmer cap is unreliable. Crystal is good. Without caps the freq is 32.773 KHz.

DS1643 implements inside similar such devices and give accuracy of about one minute in a month at 25 deg.

Will work on it more and com back to you.

Regards