TOD Clock Synchronization in a Loosely Coupled Environment
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Circuits and a method for synchronizing and checking a plurality of time-of-day (TOD) clocks in a loosely-coupled multiprocessing system are described. Unique hardware synchronizes the low-order part of the TOD clocks, and a unique method synchronizes the high-order part in the same clocks by using carry pulses derived from an intermediate bit position in each TOD clock. The carry pulses and the oscillator pulses from each of the TOD clocks in the system are sent to the other CPUs in the system which have TOD clocks. A program settable register contains an address which can be used to select one of the TOD clocks as a master to which all other TOD clocks can be synchronized. In the case of failure of the master clock, a different TOD clock can be selected by the program.