Register Access Control Circuit for On-Chip Off-Chip Arbitration
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Solution Overview
Problem
In data processing applications, existing systems face challenges in managing and arbitrating access requests to control and status registers (CSRs) among multiple devices, leading to potential deadlocks and inefficiencies, especially when handling both on-chip and off-chip requests simultaneously.
Innovation Solution
A circuit is implemented to manage access requests to CSRs, featuring a control circuit that detects completion status of off-chip requests, allowing selective forwarding or suspension of off-chip requests while independently processing on-chip requests, and using a master bus to connect on-chip devices, with an interface circuit to forward completion status and update registers, and providing backpressure signals to manage access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple devices access CSRs simultaneously through shared buses, then data processing throughput is improved, but deadlocks and access conflicts occur
Solution Approach 1:
The patent segments the access request management by separating on-chip and off-chip request handling paths. The control circuit identifies request types and routes them through different processing sequences, allowing on-chip devices to access CSRs independently of off-chip device status, thus preventing deadlocks while maintaining high throughput
Solution Approach 2:
The control circuit performs preliminary identification of request types (on-chip vs off-chip) before forwarding requests to CSRs. By detecting the completion status of off-chip requests in advance and preparing appropriate routing decisions, the system prevents access conflicts before they occur, enabling simultaneous independent access paths
2Reliability
If off-chip request completion is waited before forwarding subsequent requests, then request ordering is maintained, but access latency increases
Solution Approach 1:
The control circuit dynamically adjusts request forwarding behavior based on request type. For on-chip requests, forwarding occurs independently of off-chip completion status, minimizing latency. For off-chip requests, the circuit maintains ordering by waiting for completion status when necessary. This dynamic adaptation resolves the contradiction between ordering reliability and access speed
3Productivity
If separate handling paths are created for on-chip and off-chip requests, then access efficiency is improved, but circuit complexity increases
Solution Approach 1:
The control circuit implements a universal request handling mechanism that processes both on-chip and off-chip requests through a single integrated structure. By using a unified control logic that dynamically routes requests based on type identification, the patent achieves separate handling efficiency without requiring completely separate physical paths, thus limiting complexity increase
Data Source
AI summary
A circuit manages and controls access requests to a register, such as a control and status register (CSR) among a number of devices. In particular, the circuit selectively forwards or suspends off-chip access requests and forwards on-chip access requests independent of the status of off-chip requests. The circuit receives access requests at a plurality of buses, one or more of which can be dedicated to exclusively on-chip requests and/or exclusively off-chip requests. Based on the completion status of previous off-chip access requests, further off-chip access requests are selectively forwarded or suspended, while on-chip access request are sent independently of off-chip request status.