Browse Prior Art Database

Real-Time Clocks and Timers Architecture

IP.com Disclosure Number: IPCOM000118016D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 86K

Publishing Venue

IBM

Related People

Ebina, T: AUTHOR [+6]

Abstract

Disclosed is a method for defining hierarchical clocks and timers. Child clocks inherit certain properties of parent clocks and all single shot and periodic timers are handled by the underlying physical clock.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Real-Time Clocks and Timers Architecture

      Disclosed is a method for defining hierarchical clocks and
timers.  Child clocks inherit certain properties of parent clocks and
all single shot and periodic timers are handled by the underlying
physical clock.

      This disclosure builds upon concepts which define logical
clocks and their use in synchronization.

      This disclosure first adds the concept of hierarchical logical
clocks.  This means that a logical clock can define another logical
clock as its base clock.

      In the above illustration, logical clocks 2 & 3 (LC2, LC3) are
based upon logical clock 1 (LC1).

      The advantage of this structure is that the child logical
clocks (LC2 & LC3) can inherit certain properties and states from the
parent clock in a consistent and synchronous manner, yet have certain
different properties of their own.  For example, one child clock
might represent a different time zone from the parent while the
second child  clock may be undergoing frequent adjustments to keep it
synchronized with some other external clock.

      However, having the same parent allows both the children to
share certain properties with the parent.  For example, if the parent
is adjusted because of daylight savings time, all the child clocks
will synchronously be adjusted with it.

      Secondly, this disclosure defines the ability to define single
shot and repeating timers on any of the clocks.  Single-shot timers
are those which will occur only once.  Periodic timers are those
which will  continue to occur at a specified interval.

      All the timer events are defined using the same underlying
physical clock and done in such a way that the underlying physical
hardware need only support the ability to determine when the next of
all the scheduled timer events will occur.

      The logical clocks are defined such that the absolute time of
the clock is defined in terms of its base epoch (what date and time
the value 0 represents) and rate (T = Epoch +Rate*t).  This allows
different clocks to have different base epochs, diff...