Minimum latency tie-breaking arbitration logic circuitry

Claim 1

Arbitration means for selecting which one of a plurality of requestors is to be granted access to a commonly shared means, said arbitration means comprising: a counting means for each requestor for providing binary count output signals indicative of how long its corresponding requestor has been waiting for access; means for periodically advancing each counting means in response to an access request from its respective requestor from an initial count until its respective requestor is granted access, the advancement of each counter occurring independently of access requests from other requestors; combinational logic means to which said binary count output signals from said counters are applied for producing a binary selection signal corresponding to each requestor, said combinational logic means being operative in response to the applied binary count output signals for activating a selection signal of a corresponding selector when no other of said requestors has been waiting longer for access; and tie-breaking logic means to which the selection signals from said combinational logic means are applied for producing a grant signal corresponding to each requestor, said tie-breaking logic means being operative in response to the applied selection signals to activate none of the grant signals when none of the applied selection signals are activated and to activate only one grant signal when one or more selction signals are activated.

Claim 12

A method for selecting which one of a plurality of requestors will be granted access to a commonly shared means, said method comprising: producing a periodically occurring clock signal for defining clock periods; for each requestor, counting beginning at an initial count value the number of clock signals for which the requestor is requesting access without access being granted, the count value reached during each clock period being indicative of how long the corresponding requestor has been waiting for access; for each requestor, activating a corresponding selection signal during each clock period when no other of said requestors has been waiting longer for access; during each clock period, activating no more than one grant signal and then only if at least one selection signal is activated during that clock period, the grant signal which is activated during a clock period corresponding to the selection signal which is activated during that clock period if only one selection signal is activated, and corresponding to one of the selection signals activated during that clock period if more than one selection signal is activated during that clock period.

Claim 13

A method for selecting which one of a plurality of requestors will be granted access to a commonly shared means, said method comprising: producing a periodically occurring clock signal for defining clock periods; for each requestor, counting beginning at an initial count value the number of clock signals for which the requestor is requesting access without access being granted, the count value reached during each clock period being indicative of how long the corresponding requestor has been waiting for access; for each requestor, activating a corresponding selection signal during each clock period when no other of said requestors has been waiting longer for access; during each clock period, activating no more than one grant signal and then only if at least one selection signal is activated during that clock period, the grant signal which is activated during a clock period corresponding to the selection signal which is activated during that clock period if only one selection signal is activated, and corresponding to one of the selection signals activated during that clock period if more than one selection signal is activated during that clock period.