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Browse Prior Art Database

Timing Management in Large Real Time Systems

IP.com Disclosure Number: IPCOM000076363D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Bernard, F: AUTHOR

Abstract

This timing management system, for a large number of users, maintains a unique clock in absolute time. The system is provided with as many chains as number of standard delays, the standard delay being the time elapsed between the request and the due time.

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Timing Management in Large Real Time Systems

This timing management system, for a large number of users, maintains a unique clock in absolute time. The system is provided with as many chains as number of standard delays, the standard delay being the time elapsed between the request and the due time.

Many real-time systems, for example telephone exchange systems, involve a large number of users (by the hundreds), who may independently emit a Time Request Signal. The user must receive a Warning Signal after a given delay, specified by this Time Request Signal, but chosen among a limited number of possible delays (The "User" is not necessarily a human user, but it can be, for example, a program). The use of as many clocks or counters as possible active users would be too costly. The present system replaces the clocks or counters by very simple items ("timers") working in cooperation with a unique clock.

The Timing Management System includes the following units: - a clock, which indicates the absolute time - a Time Class Table, which indicates, for each delay class: the delay duration (in basic clock time units), the "delay shift", i.e. the rank of the leftmost insignificant bit, the HEAD (identification of the first "timer" in the chain corresponding to the delay class) and the TAIL (identification of the last "timer" of the chain), - a "Timer Pool" comprising a number of "timers". Each timer is a group of four memory fields. A timer can be active (i.e. assigned to a user) or idle. The active timers assigned to users requesting signals with the same delay class are chained: so there are as many chains as delay classes. The four fields of an active timer contain, respectively: - a pointer FROM, identifying the preceding timer in the chain (this pointer is equal to 0 in the first timer of a chain), - a pointer TO, identifying the next timer in the chain (this pointer is equal to O in the last timer of the chain), - the name of the user the timer is assigned to, - the time when the signal must be sent to this user.

The idle timers constitute a particular chain; they contain solely the pointer TO. The identity of the first timer of the idle chain is registered in a location designated by "FREETIM".

Besides, it is stated that the real-time system in which the present Timing Management System is included contains a "User Control Block", which lists information concerning the users, and in particular the identity of the assigned timers, if any. The system operates...