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Method for bus arbitration with flow control

IP.com Disclosure Number: IPCOM000020330D
Publication Date: 2003-Nov-12
Document File: 2 page(s) / 33K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for bus arbitration with flow control. Benefits include improved functionality and improved performance.

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Method for bus arbitration with flow control

Disclosed is a method for bus arbitration with flow control. Benefits include improved functionality and improved performance.

Description

         The disclosed method is bus arbitration that improves bus utilization when flow control would otherwise block the bus. The method prevents one backed-up receiver from blocking traffic for other receivers on the bus.
         In the simplest case, a bidirectional bus connects two components. The bus includes a mechanism to delay transmission to prevent data overrun. The receiver halts the sender by asserting the Full signal until the receiver is ready to accept more data.
         For example, nodes A and B are connected through a bidirectional bus. Node A is responsible for bus arbitration and sets the bus direction through the request and grant lines. Node B can only send if it asserts the request and subsequently receives a grant from node A. The strobe and data lines are bidirectional and can be driven from either A or B, depending on the bus grant state (see Figure 1).
         Assume that A is sending data to B. If B is temporarily unable to accept more data, it asserts the FullB signal. Conventionally, the bus would be blocked as long as FullB is asserted. The data transfer must be blocked in one direction. No requirement exists to prevent B from sending data to A. As a result, the disclosed method checks the request signal. If it is asserted, the A to B transfer is temporarily asserted, and the grant is given to node B. If the B to A transfer is suspended due to the assertion of FullA, the bus grant can revert back to A if FullB is cleared.
         In one implementation, messages are passed over the bus in the form of packets. Typically, the bus direction only changes at packet boundaries after an entire packet is transmitted....