Patent
1995-03-30
1998-07-21
Chung, Phung
G06F 1120
Patent
active
057845514
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to the field of processing control systems and more specifically to a duplicate control and processing unit for telecommunications equipment.
For the sake of simplicity the control and processing unit is indicated hereinafter only as the control unit.
As known, the great success of microprocessors has greatly facilitated implementation of the control unit for telecommunications equipment having even considerable complexity, as for example telephone equipment. It can also be stated that, thanks to microprocessors, the hardware design of a control unit is today nearly independent of the peculiarities of the equipment which said units supervise. Indeed, in the greater part of the known examples of microprocessor control units operating in equipment having a certain complexity, the control unit generally comprises: control of the equipment, processed during normal operation thereof, interfaces between the processing unit and the rest of the equipment. The latter can be in turn all or partly duplicated.
The processing unit can be more or less sophisticated but in turn generally includes: of course a microprocessor with the appropriate integrated circuits which co-operate with it in some functions, as for example the management of interrupts, direct access to the memory, etc.; a RAM containing the programmes for control of the entire set of equipment; an optional circuit generating parity bits on the signals which transit through the microprocessor bus; and finally a diagnostic circuit which detects access errors of the processor and processes the alarms of the equipment generated in case of failure. In some cases the processing unit includes two or more optionally synchronised microprocessors.
The designation `peripheral circuits` extends as known generally to all the circuits which equip the processing unit and convert it into an actual control unit, i.e.: extension of the processor bus, characterise more specifically the type of equipment, such as for example telephones or multiplex PCM for telephone exchanges, to include also the data RAM mentioned above together with the related interfacing circuits towards the processing unit.
It is also known that a microprocessor control unit exerts its control action on the equipment by means of selective writing operations of particular bit configurations into special registers for control of the equipment called `control points`, and selective reading operations from special state registers called `sense points`. Writing of the control points serves to control certain operational modes of the various parts which make up the equipment, while reading of the sense points serves the control unit to verify the operating state thereof.
In the last decade, particularly in the telecommunications industry, equipment characterised by high reliability and availability, produced as known by the introduction of redundancy criteria, has become more and more requested. One of said criteria, which has found greater application in practice consists of duplicating the entire control unit. The duplication involves necessarily also the code and data on which the individual processing units operate.
While duplication of the control unit contributes considerably to better reliability of equipment, it brings problems which are not found in an unduplicated control unit. These problems are principally due to the fact that there are available two processors for which it is essential to define the roles, the criteria which control the separation of duties, and the procedures for switching between them in the presence of a failure to allow one processor to take over the work carried out up to that moment by the other.
Another problem due to duplication of the control unit is that of defining how the two processors are interconnected to the rest of the equipment.
In the majority of known examples, one of the two copies of the control unit is designated the active copy, to which is entrusted the task of supervising the rest of the equipment, while the oth
REFERENCES:
patent: 5251299 (1993-10-01), Masuda et al.
patent: 5303243 (1994-04-01), Anezaki
Microsoft Press, Computer Dictionary, 1994, p. 332.
De Leva Carlo
Zambardi Maurizio
Chung Phung
Greenberg Laurence A.
Lerner Herbert L.
Siemens Telecommunicazioni S.p.A.
Vales P.
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