Method for operating and apparatus for a back-plane supporting redundant circuit cards
View Patent ↗The present invention provides clear and robust arbitration of which of two system controllers is in control of a telecommunications switching system. Each system controller monitors and actively reports its status to a separate arbitration circuit. The resultant signal from the arbitration circuit tells the system which controller to obey. By feedback of its own output unnecessary switching or ill-defined control states are avoided. In particular, if either both or neither system controllers is reporting itself as OK, the system does not switch controllers. In addition, the arbitration circuit is fed redundant clock signals and support, making it effectively redundant.
1. An apparatus for supporting a first system control circuit card and a second system control circuit card capable of providing substantially identical functions as said first system control circuit card, on a common backplane of a microprocessor-based telecommunications switching system containing a plurality of circuit boards, said apparatus comprising:
a system control panel;
first signaling means capable of conveying a first OK status signal indicative of said first system control circuit card's operational status to said system control panel;
second signaling means capable of conveying a second OK status signal indicative of said second system control circuit card's operational status to said system control panel;
arbitration means capable of comparing said first OK status signal and said second OK status signal and producing a resultant signal, said arbitration means being supplied with a plurality of clock signals and power sources; and,
switching means capable of using said resultant signal to cause said telecommunications switching system to select to use one of said first system control circuit card and a second system control circuit card;
wherein said arbitration means feeds said resultant signal output from said arbitration means back as an input to said arbitration means in order to determine which of said first system control circuit card and said second system control card is a current system controller and ensure that when said first OK status signal and said second OK status signal are either both true or both false, said current system controller remains as said current system controller.
2. The apparatus of claim 1 wherein said telecommunications switching system is digital.
3. The apparatus of claim 2 wherein said first signaling means and said second signaling means comprise software set bits.
4. The apparatus of claim 3 wherein said switching means includes eventing means capable of informing all elements of said circuit boards in said telecommunications switching system requiring knowledge of said switching, which of said redundant circuit cards to select to use.
5. The apparatus of claim 4 wherein said switching means includes interrupt means for generating an interrupt signal to all said elements of said circuit boards in said telecommunications switching system, said interrupt signal causing initialization and data auditing of said circuit boards.
6. A method for supporting a first system control circuit card and a second system control circuit card capable of providing substantially identical functions as said first system control circuit card, on a common backplane of a microprocessor-based telecommunications switching system containing a plurality of circuit boards, and a system control panel with arbitration circuitry, said arbitration circuitry being capabable of signaling said plurality of circuit boards to select to use one of said first system control circuit card and said second system control circuit card, said method comprising the steps of:
a. signaling a first OK status signal indicative of said first system control circuit card's operational status to said system control panel and a second OK status signal indicative of said second system control circuit card's operational status to said system control panel;
b. supplying said arbitration circuitry with a plurality of power sources;
c. arbitrating by using said arbitration circuitry and a plurality of clock signals to compare said first OK status signal and said second OK status signal and producing a resultant signal;
d. feeding said resultant signal output from said arbitration means back as an input to said arbitration means in order to determine which of said first system control circuit card and said second system control circuit card is a current system controller and ensure that when said first OK status signal and said second OK status signal are either both true or both false, said current system controller remains as said current system controller; and
e. utilizing said resultant signal to cause said telecommunications switching system to select to use one of said first system control circuit card and a second system control circuit card.
7. The method of claim 6 wherein said communications system is digital.
8. The method of claim 7 wherein said signaling step (a) includes:
e. the step of providing software set bits.
9. The method of claim 8 wherein said utilizing step (c) further includes:
the step of interrupting said circuit boards in said telecommunications switching system, said interrupting causing initialization and data auditing on said circuit boards.