Importance

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Abstract

A conditional carry scheduling unit that performs a scheduler carry operation for a round robin scheduler that schedules communication among a plurality of clients who compete to use a shared resource. Each client asserts a request bit to request use of the shared resource, and receives a grant bit from the round robin scheduler that is asserted when the client is scheduled to use the shared resource. The conditional carry scheduling unit includes a plurality of 2-bit carry generation units that operate in parallel. Within each of the 2-bit carry generation units except the initial carry generation unit, two conditional output signals are produced and supplied to a multiplexer tree. The initial carry generation unit assumes a carryin bit of zero, and outputs its carryout bit to the multiplexer tree which determines the actual carries and supplies them back to the carry generation units. Each carry generation unit includes a second multiplexer tree to select the carryout bits (the 'SC result bits') from each bit position. If the carryout bit from the final carry generation unit is zero, then the SC result bits for the initial operation provide the grant word for the current scheduling cycle, but if the carryout bit is one, the above scheduler carry operation is repeated assuming a carryin bit of one. To increase speed of operation, parallel branches may be provided, so that two scheduler carry operations can be performed in parallel and the correct grant word selected after the carryout bit is known.

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First Claim