Abstract

Embedded systems are finding widespread application including communication systems, factory automation, graphics and imaging systems, medical equipment and even household appliances. We endeavor to highlight the need for formally verifying the correctness of an embedded software, and suggest a methodology for the same using Multiway Decision Graphs (MDG). This is particularly necessary for real-time and safety critical applications. We propose a formal model for the Instruction Set Architecture, along with the underlying hardware (RT level) of a microcontroller in commercial use. The embedded software we consider is used in a mouse controller application. Models for the flowchart specification and the assembly language implementation of the embedded software are also portrayed. Using the MDG verification tools, equivalence checking experiments are conducted between the flowchart specification of the embedded software and its assembly code implementation. In addition, specific properties of the mouse controller behavior are also checked on all our models. Inconsistencies in the assembly code with respect to the specification, as published in the application notes of the manufacturer, were uncovered through both equivalence and property checking. Given the relatively small CPU time and memory consumption achieved in our experiments, the verification methodology we adopted would be able to verify significantly larger programs using the MDG tools and can hence cope with the inherent complexities of verifying a whole embedded system.

Citations