Bus System Parallel Access Control via Request Suspension
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Solution Overview
Problem
In bus systems, the efficiency of data transfer is reduced due to the need to suspend subsequent requests until responses to previous requests are received, which can lead to unordered responses from slaves, and existing solutions like buffers increase circuit size and complexity.
Innovation Solution
A bus system with a determination unit that allows the master to issue subsequent requests before receiving responses from previous ones, using a suspension unit to manage request transfers based on notification from slaves regarding processing status, thereby ensuring response order without the need for large buffers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the master suspends issuance of requests to different slaves until a response to a previous request is returned, then the order of responses is guaranteed, but the data transfer efficiency is reduced
Solution Approach 1:
The determination unit performs preliminary determination about whether to permit transfer of subsequent requests before actually transferring them. This allows the system to proactively prevent out-of-order responses by checking if a previous request has been acknowledged, rather than waiting for responses to arrive and then reordering them. The master can issue requests in advance subject to this preliminary permission check.
2Reliability
If a buffer is used to rearrange responses from slaves into expected order, then the response order is guaranteed, but the circuit size is greatly increased
Solution Approach 1:
The invention extracts the order guarantee function from the response data path and places it in the request control path. Instead of buffering and rearranging response data (which would require large buffers), the system extracts and enforces ordering constraints at the request level using the determination unit. This separates the control function from the data function, avoiding the need for large buffers.
Solution Approach 2:
The determination unit acts as an intermediary between the master and slaves, mediating the request transfer process. It receives notifications from slaves about request processing and uses this information to control whether subsequent requests are permitted to transfer. This intermediary enforces ordering without requiring buffers at the master or slave ends.
3Productivity
If parallel access to multiple slaves is permitted, then the data transfer efficiency is improved, but the risk of out-of-order responses increases
Solution Approach 1:
The system implements feedback through notifications from slaves to the determination unit about request processing status. When a slave processes a request, it notifies the determination unit, which then uses this feedback information to decide whether to permit subsequent requests. This feedback mechanism enables parallel access while maintaining order because the system dynamically adjusts permission based on actual processing status.
Data Source
AI summary
A bus system comprises a master, a first slave, a second slave, and a bus. The master is configured to be able to issue a second request to the second slave after issuing a first request to the first slave and before receiving a response to the first request. The bus comprises: a determination unit configured to, upon receiving the second request, determine whether to permit a transfer of the second request to the second slave; and a suspending unit configured to suspend the transfer of the second request to the second slave while it is determined by the determination unit that the transfer is not permitted. The determination unit determines whether or not the transfer is permitted based on a notification from the first slave regarding processing of the first request.