Method and apparatus for accelerating arbitration in a serial bus by detection of acknowledge packets

In an electronics system including a serial bus, a method for arbitrating for control of the serial bus by a node of the serial bus comprising the steps of:

• detecting a packet on the serial bus by the node;
• determining a length of the packet by the node;
• comparing the length of the packet to a first length by the node;
• requesting control of the serial bus by the first node before a subaction gap time has elapsed if comparing the length of the packet to the first length indicates that the packet is an acknowledge packet;
• and
• requesting control of the serial bus by the first node after the subaction gap time has elapsed if comparing the length of the packet to the first length indicates that the packet is a data packet.

In a bus having a plurality of nodes, a node comprising:

• at least one port coupled to transmit and receive data on the bus;
• a node interconnect coupled to the port, the node interconnect being operative to transfer packets between the port and a local host of the node;
• a counter coupled to the node interconnect, the counter being operative to determine a length of a packet transmitted via the node interconnect;
• an arbiter coupled to the counter and the node interconnect, the arbiter being operative to compare the length of the packet as determined by the counter to a first length, wherein the arbiter is operative to request control of the bus before a predetermined length of time has elapsed if comparing the length of the packet to the first length indicates that the packet is a first type of packet, and wherein the arbiter is operative to request control of the bus after the predetermined length of time has elapsed if comparing the length of the packet to the first length indicates that the packet is a second type of packet.

A serial bus comprising:

• a plurality of nodes;
• a plurality of point-to-point links, wherein each point-to-point link is coupled between two nodes in a manner such that each node is coupled to every other node via one or more point-to-point links,
• wherein at least one node of the plurality of nodes is an accelerated arbitration node comprising:
• at least one port coupled to a point-to-point link and operative to transmit and receive data via the point-to-point link;
• a node interconnect coupled to the port, the node interconnect being operative to transfer packets between the port and a local host of the accelerated arbitration node;
• a counter coupled to the node interconnect, the counter being operative to determine a length of a packet transmitted on the serial bus by the accelerated arbitration node via the node interconnect;
• an arbiter coupled to the counter and the node interconnect, the arbiter being operative to compare the length of the packet as determined by the counter to a first length, wherein the arbiter is operative to request control of the bus before a predetermined length of time has elapsed if comparing the length of the packet to the first length indicates that the packet is an acknowledge packet, and wherein the arbiter is operative to request control of the bus after the predetermined length of time has elapsed if comparing the length of the packet to the first length indicates that the packet is a data packet.