Distributed bus arbitration according each bus user the ability to inhibit all new requests to arbitrate the bus, or to cancel its own pending request, and according the highest priority user the ability to stop the bus

A digital communication system including a digital communication bus and a plurality of bus User devices interconnected to said bus by a like plurality of identical bus interface logic circuits, each said bus interface logic circuits comprising:

• arbitration logic means for, responsively to an associated said bus User device, entering into arbitrating for ownership of said bus by transmitting the true state of an associated arbitration signal, called a REQUEST signal, upon an associated one of a plurality of first signal lines of said bus, and for, responsively to the receipt of arbitration signals upon said plurality of first signal lines of said bus, determining whether arbitration is won and ownership of said bus is obtained IN ORDER THAT IF arbitration is not won THEN continuing said transmitting of said true state of said associated arbitration signal, ELSE if arbitration is won ceasing said transmitting of said true state of said associated arbitration signal;
• arbitration inhibit transmitter logic means responsive to said associated said bus User device for transmitting the true state of an arbitration inhibit signal, called a REQUEST INHIBIT signal, upon a second signal line of said bus until such time as arbitration is won;
• and
• arbitration inhibit receiver logic means for receiving said true state of said arbitration inhibit signal, said REQUEST INHIBIT signal, upon said second signal line of said bus and responsively thereto for causing the suspension of only said entering into said arbitrating for ownership of said bus for the duration of said true state of said arbitration inhibit signal, while not causing any effect upon said determining, said continuing said transmitting, and said ceasing said transmitting;
• whereby since each said bus interface logic circuits does not transmit said true state of said arbitration inhibit signal save while arbitrating for ownership of said bus, then said receiving of said true state of said arbitration inhibit signal by the selfsame said bus interface logic circuit which is transmitting said true state of said arbitration inhibit signal is without effect, said selfsame said bus interface logic circuit having already done said entering into arbitrating for ownership of said bus;
• whereby said receiving of said true state of said arbitration inhibit signal at any said bus interface logic circuits does only cause said suspension of said entering into arbitration, and does not effect said continuing arbitrating of these said bus interface logic circuits as have already, at the time of said receipt of said arbitration inhibit signal, entered into said arbitrating.

In a digital communication system including a digital communication bus and a plurality of bus User devices communicably interconnected to said bus by a like plurality of bus interface logic circuits, an improvement to said bus interface logic circuit according said associated bus User device the ability to both initiate the request, and retract the request previously initiated, which request does cause said bus interface logic circuit to engage in arbitration for ownership of said digital communication bus on behalf of said associated bus User device, said improvement to the apparatus of said bus interface logic circuit according that said request to engage in arbitration should be both initiatable and retractable by said associated bus User device comprising:

• request flip-flop logic means responsive to a first, initiate, signal from said associated bus User device for registering a request to arbitrate said digital communication bus by setting, and responsive to a second, retract signal from said associated bus User device for deregistering any request to arbitrate said digital communication bus by clearing;
• and
• arbitration logic means responsive to said request flip-flop logic means which is enabled to communicate control signals to said bus for arbitrating for ownership of said digital communication bus when said request flip-flop logic means is in one state, and which is disabled when said request flip-flop logic means is in its other state;
• whereby said arbitrating amongst and between said like plurality of bus interface logic circuits, which arbitrating is thus distributed amongst and between said bus interface logic circuits, is enabled or disabled to be engaged in by said arbitration logic means within and at each one of said bus interface logic circuits by said set or said clear condition of said request flip-flop logic means and at each said one of said bus interface logic circuits;
• whereby the process of arbitration which is distributed is, nonetheless to said distribution, not only enterable but also exitable at each one of said bus interface logic circuits.

In a digital communication system including a digital communication bus and a plurality of bus User devices communicably interconnected to said bus by a like plurality of bus interface logic circuits, an improvement to said bus interface logic circuit in order to cause said bus interface logic circuit to constantly and continuously arbitrate for ownership of said bus while simultaneously preventing said bus interface logic circuit from notifying said associated one of said plurality of bus User devices, and also preventing the transmission of information until such time that said bus interface wins arbitration for ownership of said bus, said improvement to the apparatus of said bus interface logic circuit to the end that is should continuously arbitrate but not act upon the winning of arbitration comprising:

• arbitration logic means responsive to an external signal, called STOP BUS, to constantly and continuously arbitrate for ownership of said bus regardless of whether said associated one of said plurality of bus User devices has directed entrance into arbitration and regardless of whether arbitration is, at a time or times, won;
• inhibiting-of-bus-granted logic means responsive to said external signal for causing that said associated one of said plurality of bus User devices will not be notified of the winning of arbitration by a signal arising at said arbitration logic means upon any of said time or times at which arbitration is won;
• and
• inhibiting-of-further-information-transmission logic means responsive to said external signal for causing that no transmission of any information such as data will occur responsively to, and upon, said time or times at which arbitration is won;
• whereby said bus interface logic circuit is caused, responsively to said external signal, to continuously arbitrate for ownership of said bus, while also being caused not to act to notify said associated one of said plurality of bus User devices, and also not to act to transmit information upon the winning of arbitration;
• whereby when that said bus interface logic circuit caused, responsively to said external signal, to continuously arbitrate for said bus but not to act upon the winning of arbitration is the single highest priority one bus interface logic circuit of all said plurality of bus interface logic circuits as may at times arbitrate, then said continuously arbitrating single highest priority one bus interface logic circuit will continuously win arbitration but will not act upon the winning of arbitration, which occurrence will stop the use of the bus by any and all bus User devices for the transmission of any information such as data.

Upon a digital communications bus interconnecting a multiplicity of bus User devices each interconnected to said bus through like bus interface logics, an improved method of conducting distributed arbitration for ownership of said bus amongst and betweenst said bus User devices to the end that each User device may temporarily inhibit any new, previously uncommenced, entrance into said distributed arbitration of other bus interconnected said User devices, said method comprising:

• a first one of said multiplicity of bus User devices does firstly enter into distributed arbitration for ownership of said bus by causing the associated one said bus interface logics to raise an associated one REQUEST signal upon an associated one line thereof of said bus for the purpose of participating in said arbitration as a bus User device desiring ownership thereof of said bus;
• and
• at some time during the continuing maintenance of said one REQUEST signal, which signal does persist until said first one of said multiplicity of bus User devices does win said distributed arbitration, said first one of said multiplicity of bus User devices does also cause said associated one of said bus interface logics to raise a REQUEST INHIBIT signal on a dedicated one signal line thereof of said bus;
• then
• at least a one or ones of said bus interface logics as are associated with second one or ones of said multiplicity of bus User devices does (do) sense said raised REQUEST INHIBIT signal and, responsively thereto during the duration of said raised REQUEST INHIBIT signal, does (do) preclude that said associated second one or ones of said multiplicity of bus User devices is (are) able to firstly, meaning newly, enter into said distributed arbitration;
• then
• said first one of said multiplicity of bus User devices which did cause said associated one of said bus interface logics to raise said REQUEST INHIBIT signal does eventually, in priority order, win arbitration and, responsively thereto, said associated one of said bus interface logics does lower said REQUEST INHIBIT signal;
• wherein the effect of said first one of said multiplicity of bus User devices in causing said raising of said REQUEST INHIBIT signal was to suspend during the duration of said REQUEST INHIBIT signal the new entrance into said distributed arbitration of said second one or ones of said multiplicity of bus User devices as was (were) not already participatory therein;
• wherein IF all ones of said bus interface logics which are associated with all ones of said multiplicity of bus User devices, including said first one of said multiplicity of bus User devices, do sense said raised REQUEST INHIBIT signal during the duration thereof, and do responsively thereto preclude that each associated one of said multiplicity of bus User devices should firstly, enter into said distributed arbitration, THEN during the duration of said raised REQUEST INHIBIT signal identities and numbers of all said multiplicity of bus User devices which are participating in said distributed arbitration will not be subject to augmentation by the new entrance into said distributed arbitration of any one or ones of said multiplicity of bus User devices which were not, previously to the raising of said REQUEST INHIBIT signal, already participating therein said distributed arbitration, ELSE if not all of said ones of said bus interface logics do not sense said raised REQUEST INHIBIT signal then at least some of said multiplicity of bus User devices will be able, during the duration of said raised REQUEST INHIBIT signal, to newly enter into said distributed arbitration.