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Propagating Requester and Transaction IDs Across Bus Bridges

IP.com Disclosure Number: IPCOM000100573D
Publication Date: 2005-Mar-15
Document File: 2 page(s) / 263K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that enables a system connected to two physical busses to behave as a single-bus domain for sequence IDs. Benefits include simplifying the bridge design.

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Propagating Requester and Transaction IDs Across Bus Bridges

Disclosed is a method that enables a system connected to two physical busses to behave as a single-bus domain for sequence IDs. Benefits include simplifying the bridge design.

Background

Bridges are used to couple devices into two bus domains. Also, bridges can reduce the number of agents in a bus segment to alleviate bandwidth, latency, and electrical limitations. In buses supporting split transactions, sequence IDs (typically the transaction ID concatenated with the requester ID) is used to associate the address and data transfers.

General Description

In the disclosed method, the requester IDs are generated for the two busses independently (see Figure 1). In this approach, the bridge is also considered a bus agent with two requester IDs
(i.e. one per bus). For example, in one scenario agent 1 is connected to bus A and generates a read request targeting agent 3, which is connected to bus B. After the bridge claims the transaction on bus A, it generates the same transaction on bus B, but with the bus B requester ID and a new transaction ID (sequence ID). Once agent 3 (on bus B) accepts the transaction, it provides read data using the same sequence ID. The bridge accepts read data, and uses the original sequence ID (i.e. the sequence ID generated by agent 1 on bus A) to provide read data to agent 1 on bus A. Therefore, if the IDs for agents connected to the two busses (bus A and bus B) are generated independently, t...