Improving the LEON Spacecraft Computer Processor for Real-Time Performance Analysis

摘要

This paper presents an enhanced version of the LEON architecture with a performance-monitoring unit, including performance counters for different events and a trace buffer. Through this enhancement the user or system engineer is able to obtain information about the cache behavior and the execution path of a whole program or a fragment of code. This development introduces several advantages over simulators, such as allowing tests to be performed directly on the real target in a nonintrusive mode. Taking advantage of this enhancement, a suite of tests for cache characterization and evaluation has been developed. The results of this study can contribute to modeling the behavior of the LEON architecture in areas such as worst-case execution-time estimation and probabilistic analysis. The new features can be very useful during the validation and verification phase of the real-time software, supporting code coverage techniques and reducing the execution-time variability due to hardware effects such as cache and pipelines. The field-programmable gate-array resources employed by the performance-monitoring unit developed in this paper are low, on the order of 3-5%, with the exception of an increase of 37% in the use of embedded memory blocks.