Command Arbitration Using Time Stamp Tournament and History
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Solution Overview
Problem
Existing semiconductor integrated devices face challenges in efficiently arbitrating commands for shared resources like shared memories, particularly in prioritizing and minimizing latency, which affects power efficiency and access efficiency.
Innovation Solution
A data processing apparatus that assigns time stamps to commands and increments them with each arbitration cycle, using a scheduler to select commands based on the largest time stamp value in a tournament manner, and utilizing a command selection history when time stamp values are equal, to ensure uniform processing and prevent priority starvation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time stamp values are used for command arbitration, then command selection is simplified, but latency increases when time stamp values are equal
Solution Approach 1:
The system pre-assigns time stamp values to commands at the time of reception and stores them in advance. When arbitration is needed, the pre-stored time stamps are immediately available for comparison, eliminating the need for real-time timestamp generation and reducing arbitration latency.
Solution Approach 2:
The system creates a copy of the time stamp value and stores it in a register along with the command. This allows the arbitration logic to compare time stamp copies without affecting the original command timing information, enabling fast comparison while preserving accurate timing data.
2Ease of operation
If commands with equal time stamp values are processed in arbitrary order, then processing is simpler, but priority starvation occurs
Solution Approach 1:
The system uses a feedback mechanism where the arbitration result (which command was selected) is fed back to update the selection history. When time stamp values are equal, this feedback ensures that previously selected destinations are given priority again, preventing any single destination from being continuously starved of service while maintaining simple processing logic.
3Productivity
If tournament-style comparison is used for command selection, then arbitration is more efficient, but device complexity increases
Solution Approach 1:
The arbitration process is segmented into multiple comparison stages, with each stage handling a subset of commands. This segmentation allows the complex tournament-style arbitration to be broken down into simpler, manageable comparison steps, improving efficiency while making the overall structure more implementable.
Solution Approach 2:
The system merges the time stamp comparison function with the command arbitration logic into a unified arbitration unit. By combining these functions, the tournament-style comparison can be performed efficiently within a single integrated structure rather than requiring separate timestamp management and arbitration modules.
Data Source
AI summary
A data processing apparatus includes a master device configured to transmit commands for destinations, a slave device including a plurality of command processing regions respectively corresponding to the destinations, and a controller configured to relay communication between the master device and the slave device. The controller assigns time stamp value to the commands as an initial value when the commands was received by the controller and increment the time stamp value every command arbitration cycle, selects a command having a largest time stamp value among the commands in a tournament manner by comparing commands having different destinations every command arbitration cycle, stores a command selection history of each comparison of commands, selects the command based on a command selection history corresponding to the compared commands when respective time stamp values of the compared commands are the same or substantially the same as each other.