Apparatus and method for sharing variables and resources in a multiprocessor routing node

A communication network comprising a plurality of routers that communicate data packets to one another and to interfacing external devices, each of said plurality of routers comprising:

• a switch fabric;
• and
• R routing nodes coupled to said switch fabric, each of said R routing nodes capable of exchanging data packets with said external devices and with other ones of said R routing nodes via said switch fabric, wherein a first of said R routing nodes comprises:
• an inbound network processor comprising a first plurality of micro engines capable of forwarding incoming data packets from external ports to said switch fabric;
• an outbound network processor comprising a second plurality of micro engines capable of forwarding outgoing data packets from said switch fabric to said external ports;
• and an asynchronous variables circuit for controlling access of said inbound and outbound network processors to at least one of i) a shared resource and ii) a shared variable in said router, wherein said asynchronous variables circuit further comprises a second register storing control and status bits that control read access and write access to first data value in a first register, and said control and status bits comprise a full flag and an empty flag indicating whether a state of said first data value in said first register is one of:
• i) uninitialized;
• ii) empty;
• iii) full, and iv) undefined, wherein said first data value may not be read in a protected mode when said full flag and empty flag indicate that said first data value is in an empty state.

For use in a router comprising a plurality of routing nodes, wherein a first routing node comprises:

• i) an inbound network processor that forwards incoming data packets from external ports to a switch fabric, and ii) an outbound network processor that forwards outgoing data packets from the switch fabric to the external ports, a method of controlling access to resources and variables shared by the inbound and outbound network processors, the method comprising the steps of:
• reading a first data value from an asynchronous variables circuit that controls access to at least one of i) a shared resource and ii) a shared variable in said router;
• and
• setting at least one control/status bit that controls read access and write access to the first data value in asynchronous variables circuit, wherein the at least one control/status bit comprises a full flag and an empty flag indicating whether a state of the first data value, and wherein the first data value may not be read in a protected mode when the full flag and the empty flag indicate that the first data value is in an empty state wherein the full flag and the empty flag indicate whether a state of the first data value is one of:
• i) uninitialized;
• ii) empty;
• iii) full, and iv) undefined and the inbound network processor comprises a plurality of microengines.